rgw/sfs: segfault when running 's3tests_boto3.functional.test_s3.test_post_object_*'

[jecluis]

Reproducible with
nosetests -v -s <TEST>

with test being any of the below:

 s3tests_boto3.functional.test_s3:test_post_object_set_success_code
 s3tests_boto3.functional.test_s3:test_post_object_set_invalid_success_code
 s3tests_boto3.functional.test_s3:test_post_object_upload_larger_than_chunk

Really, any test from s3tests_boto3.functional.test_s3:test_post_object_* is expected to fail.

     0> 2022-10-27T09:02:44.905+0000 7f8e6eaf46c0 -1 *** Caught signal (Segmentation fault) **
 in thread 7f8e6eaf46c0 thread_name:radosgw

 ceph version 3gw-20220804-71-g771bbfc8cee (771bbfc8cee56915e58dd2af86b57ae29da7bc45) quincy (dev)
 1: /lib64/libc.so.6(+0x3d910) [0x7f8ea9120910]
 2: (rgw::sal::SFSAtomicWriter::complete(unsigned long, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::chrono::time_point<ceph::real_clock, std::chrono::duration<unsigned long, std::ratio<1l, 1000000000l> > >*, std::chrono::time_point<ceph::real_clock, std::chrono::duration<unsigned long, std::ratio<1l, 1000000000l> > >, std::map<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, ceph::buffer::v15_2_0::list, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, ceph::buffer::v15_2_0::list> > >&, std::chrono::time_point<ceph::real_clock, std::chrono::duration<unsigned long, std::ratio<1l, 1000000000l> > >, char const*, char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const*, rgw_zone_set*, bool*, optional_yield)+0x5bb) [0x7f8eabe0ed9b]
 3: (RGWPostObj::execute(optional_yield)+0x14a9) [0x7f8eab918c09]
 4: (rgw_process_authenticated(RGWHandler_REST*, RGWOp*&, RGWRequest*, req_state*, optional_yield, rgw::sal::Store*, bool)+0xd0a) [0x7f8eab49679a]
 5: (process_request(rgw::sal::Store*, RGWREST*, RGWRequest*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, rgw::auth::StrategyRegistry const&, RGWRestfulIO*, OpsLogSink*, optional_yield, rgw::dmclock::Scheduler*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*, std::chrono::duration<unsigned long, std::ratio<1l, 1000000000l> >*, std::shared_ptr<RateLimiter>, int*, rgw::lua::Background*)+0x2414) [0x7f8eab499554]
 6: /lib64/libradosgw.so.2(+0x8fe28c) [0x7f8eab3ef28c]
 7: /lib64/libradosgw.so.2(+0x8fef37) [0x7f8eab3eff37]
 8: make_fcontext()
 NOTE: a copy of the executable, or `objdump -rdS <executable>` is needed to interpret this.