[YSQL][PgstatCollector][TSan] ThreadSanitizer: data race in reaper

[def-]

Jira Link: DB-944

Description

Similar to #11701 , but happens not during cancel but with reaper:

WARNING: ThreadSanitizer: data race (pid=14841)
  Read of size 4 at 0x7fe21a843714 by thread T1:
    #0 pgstat_start <null> (postgres+0xa0dccf)
    #1 reaper <null> (postgres+0xa48307)
    #2 __tsan::CallUserSignalHandler(__tsan::ThreadState*, bool, bool, bool, int, __sanitizer::__sanitizer_siginfo*, void*) <null> (postgres+0x4ca7b0)
    #3 ServerLoop <null> (libyrpc.so+0x1aeec5)
    #4 PostmasterMain <null> (libyrpc.so+0x1af0dd)
    #5 PostgresServerProcessMain <null> (libyrpc.so+0x1b1445)
    #6 boost::asio::detail::scheduler::run(boost::system::error_code&) <null> (libyrpc.so+0x1b1104)
    #7 main <null> (libyrpc.so+0x1b3ada)
    #8 realloc <null> (libyrpc.so+0x1ac551)
    #9 read_alias_file <null> (libyrpc.so+0x1b3088)
    #10 useful_strerror <null> (libyrpc.so+0x1b2f8d)
    #11 expand_fmt_string <null> (libserver_process.so+0x96004)
    #12 errmsg <null> (libyb_util.so+0x3d7389)
    #13 pgstat_read_statsfiles <null> (postgres+0x4c4052)

  Previous write of size 4 at 0x7fe21a843714 by main thread:
    [failed to restore the stack]

  Location is global '__tsan::CallUserSignalHandler(__tsan::ThreadState*, bool, bool, bool, int, __sanitizer::__sanitizer_siginfo*, void*)' at 0x7fe2116cf000 (zero (deleted)+0x000009174714)

  Thread T1 'iotp_pggate_ybc' (tid=14844, running) created by main thread at:
    #0 realloc <null> (postgres+0x4c40d5)
    #1 yb::rpc::IoThreadPool::IoThreadPool(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, unsigned long) <null> (libyb_util.so+0x3d6b93)
    #2 yb::rpc::Messenger::Messenger(yb::rpc::MessengerBuilder const&) <null> (libyrpc.so+0x1ac3c0)
    #3 yb::rpc::IoThreadPool::Impl::Impl(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, unsigned long) <null> (libyrpc.so+0x1abd8c)
    #4 yb::rpc::MessengerBuilder::Build() <null> (libyrpc.so+0x1abb07)
    #5 PgstatCollectorMain <null> (libyrpc.so+0x1b7e57)
    #6 pgstat_start <null> (libyrpc.so+0x1b4a4a)
    #7 reaper <null> (libyb_client.so+0x3e97dc)
    #8 __tsan::CallUserSignalHandler(__tsan::ThreadState*, bool, bool, bool, int, __sanitizer::__sanitizer_siginfo*, void*) <null> (libyb_pggate.so+0xcc931)
    #9 ServerLoop <null> (libyb_pggate.so+0xcc5f7)
    #10 PostmasterMain <null> (libyb_pggate.so+0xba798)
    #11 PostgresServerProcessMain <null> (libyb_pggate.so+0xbaa37)
    #12 YBInitPostgresBackend <null> (postgres+0xc2b3ec)
    #13 InitPostgres <null> (postgres+0xc08f5c)
    #14 main <null> (postgres+0xa499aa)
    #15 realloc <null> (postgres+0x9804b5)
    #16 read_alias_file <null> (postgres+0x97f8b6)
    #17 useful_strerror <null> (postgres+0x97e6b0)
    #18 expand_fmt_string <null> (postgres+0x97b693)
    #19 errmsg <null> (postgres+0x88b017)
    #20 pgstat_read_statsfiles <null> (postgres+0x88b421)