kv/LevelDBStore: fix incorrect ceph_abort_msg() usage

kv/LevelDBStore: fix incorrect ceph_abort_msg() usage

Compile error is encountered when HAVE_LEVELDB_FILTER_POLICY is not
defined.

/ceph/src/kv/LevelDBStore.cc: In member function 'int LevelDBStore::load_leveldb_options(bool, leveldb::Options&)':
/ceph/src/kv/LevelDBStore.cc:96:22: error: invalid initialization of reference of type 'const string& {aka const std::__cxx11::basic_string<char>&}' from expression of type 'bool'ceph_abort_msg(0 == "bloom size set but installed leveldb doesn't support bloom filters");
                    ~~^~~~
/ceph/src/include/ceph_assert.h:90:69: note: in definition of macro 'ceph_abort_msg'
   ::ceph::__ceph_abort( __FILE__, __LINE__, __CEPH_ASSERT_FUNCTION, msg)
                                                                     ^~~
/ceph/src/include/ceph_assert.h:62:19: note: in passing argument 4 of 'void ceph::__ceph_abort(const char*, int, const char*, const string&)'
 [[noreturn]] void __ceph_abort(const char *file, int line, const char *func,
                   ^~~~~~~~~~~~
src/kv/CMakeFiles/kv.dir/build.make:130: recipe for target 'src/kv/CMakeFiles/kv.dir/LevelDBStore.cc.o' failed

Signed-off-by: Jerry Lee <leisurelysw24@gmail.com>