crush: Fix segfault in update_from_hook

crush: Fix segfault in update_from_hook

We create SubProcess to run script conf.crush_location_hook.
We pass arguments via add_cmd_args(const char*, ...).
One of the arguments, cct->_conf->name.get_type_str(), is string_view.
x86-64-ABI states that when struct/class is passed by value, its fields are extracted to
registers/pushed on stack.
string_view is a class with fields:
    class basic_string_view {
    ...
      size_t	    _M_len;
      const _CharT* _M_str;
    };

As a result, a 7th parameter on stack (1st is `this` of SubProcess),
is _M_len, but is it interpreted as char*, which leads to SIGSEGV.

Fixes: https://tracker.ceph.com/issues/50659
Signed-off-by: Adam Kupczyk <akupczyk@redhat.com>