osd: fix ODR violation in max_prio_map

osd: fix ODR violation in max_prio_map

The static std::map max_prio_map was defined in the osd_types.h header
file, causing every translation unit that included this header to get
its own copy of the variable. This led to One Definition Rule (ODR)
violations where multiple instances of the same variable existed at
runtime.

During program cleanup, destructors for these multiple instances would
attempt to free the same memory regions, resulting in segmentation
faults in tcmalloc/memory allocator as seen with ceph-dencoder.

This issue surfaced after a yet-merged-change which converts erasure_code
and json_spirit to OBJECT libraries. Before that change, these were
STATIC libraries that were linked via target_link_libraries. The
incorrect linkage meant their object files (and thus their copies of
max_prio_map) were kept separate and didn't conflict at runtime.

After converting to OBJECT libraries and properly incorporating them
into libceph-common.so (commit 8b0e3fb2c23), the multiple copies of
max_prio_map from different translation units all ended up in the same
shared library, exposing the ODR violation. During program exit, the
dynamic linker attempted to run destructors for all instances, leading
to double-free crashes.

Fix by moving the map into a static helper function in PeeringState.cc
(the only file that uses it). The map is now a function-local static
const variable, ensuring a single instance that is properly initialized
and destructed.

Backtrace before fix:
```
    #0  0x00007ffff7dbb1a0 in tcmalloc::ThreadCache::ReleaseToCentralCache(tcmalloc::ThreadCache::FreeList*, unsigned int, int) () from /lib/x86_64-linux-gnu/libtcmalloc.so.4
    #1  0x00007ffff7dbb57f in tcmalloc::ThreadCache::Scavenge() () from /lib/x86_64-linux-gnu/libtcmalloc.so.4
    #2  0x00007ffff6bc8aa2 in std::__new_allocator<std::_Rb_tree_node<std::pair<int const, int> > >::deallocate (this=0x7ffff7d48f78 <max_prio_map>, __p=0x555555f43890, __n=1)
    #3  0x00007ffff6bc89f9 in std::allocator<std::_Rb_tree_node<std::pair<int const, int> > >::deallocate (this=0x7ffff7d48f78 <max_prio_map>, __p=0x555555f43890, __n=1)
    #4  std::allocator_traits<std::allocator<std::_Rb_tree_node<std::pair<int const, int> > > >::deallocate (__a=..., __p=0x555555f43890, __n=1)
    #5  std::_Rb_tree<int, std::pair<int const, int>, std::_Select1st<std::pair<int const, int> >, std::less<int>, std::allocator<std::pair<int const, int> > >::_M_put_node (this=0x7ffff7d48f78 <max_prio_map>, __p=0x555555f43890)
    #6  0x00007ffff6bc892e in std::_Rb_tree<int, std::pair<int const, int>, std::_Select1st<std::pair<int const, int> >, std::less<int>, std::allocator<std::pair<int const, int> > >::_M_drop_node (this=0x7ffff7d48f78 <max_prio_map>, __p=0x555555f43890)
    #7  0x00007ffff6bc886e in std::_Rb_tree<int, std::pair<int const, int>, std::_Select1st<std::pair<int const, int> >, std::less<int>, std::allocator<std::pair<int const, int> > >::_M_erase (this=0x7ffff7d48f78 <max_prio_map>, __x=0x555555f43890)
    #8  0x00007ffff6bc8854 in std::_Rb_tree<int, std::pair<int const, int>, std::_Select1st<std::pair<int const, int> >, std::less<int>, std::allocator<std::pair<int const, int> > >::_M_erase (this=0x7ffff7d48f78 <max_prio_map>, __x=0x555555f43cb0)
    #9  0x00007ffff6bc8854 in std::_Rb_tree<int, std::pair<int const, int>, std::_Select1st<std::pair<int const, int> >, std::less<int>, std::allocator<std::pair<int const, int> > >::_M_erase (this=0x7ffff7d48f78 <max_prio_map>, __x=0x555555f43ad0)
    #10 0x00007ffff6bc8805 in std::_Rb_tree<int, std::pair<int const, int>, std::_Select1st<std::pair<int const, int> >, std::less<int>, std::allocator<std::pair<int const, int> > >::~_Rb_tree (this=0x7ffff7d48f78 <max_prio_map>)
    #11 0x00007ffff6bc7345 in std::map<int, int, std::less<int>, std::allocator<std::pair<int const, int> > >::~map (this=0x7ffff7d48f78 <max_prio_map>)
    #12 0x00007ffff484bd51 in __cxa_finalize (d=0x7ffff7d3f440) at ./stdlib/cxa_finalize.c:97
    #13 0x00007ffff6af9487 in __do_global_dtors_aux () from /home/kefu/dev/ceph/build/lib/libceph-common.so.2
    #14 0x00007ffff7fbfd20 in ?? ()
    #15 0x00007ffff7fc8fc2 in _dl_call_fini (closure_map=0x7fffffffd0f0, closure_map@entry=0x7ffff7fbfd20) at ./elf/dl-call_fini.c:43
    #16 0x00007ffff7fcbe72 in _dl_fini () at ./elf/dl-fini.c:120
    #17 0x00007ffff484c291 in __run_exit_handlers (status=0, listp=0x7ffff49f1680 <__exit_funcs>, run_list_atexit=run_list_atexit@entry=true, run_dtors=run_dtors@entry=true) at ./stdlib/exit.c:118
    #18 0x00007ffff484c35a in __GI_exit (status=<optimized out>) at ./stdlib/exit.c:148
    #19 0x00007ffff4833caf in __libc_start_call_main (main=main@entry=0x55555556cd90 <main(int, char const**)>, argc=argc@entry=2, argv=argv@entry=0x7fffffffd488) at ../sysdeps/nptl/libc_start_call_main.h:74
    #20 0x00007ffff4833d65 in __libc_start_main_impl (main=0x55555556cd90 <main(int, char const**)>, argc=2, argv=0x7fffffffd488, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffd478) at ../csu/libc-start.c:360
    #21 0x00005555555695e1 in _start ()
```

Signed-off-by: Kefu Chai <k.chai@proxmox.com>