[fix](brpc) coredump caused by brpc checking

[mrhhsg]

What problem does this PR solve?

/root/doris/be/src/runtime/fragment_mgr.cpp:1064:20: runtime error: member call on null pointer of type 'doris::PBackendService_Stub'
#0 0x55bd899c9aaa in doris::FragmentMgr::_check_brpc_available(std::shared_ptr<doris::PBackendService_Stub> const&, doris::FragmentMgr::BrpcItem const&) /root/doris/be/src/runtime/fragment_mgr.cpp:1064:20
#1 0x55bd899c521f in doris::FragmentMgr::cancel_worker() /root/doris/be/src/runtime/fragment_mgr.cpp:1021:13
#2 0x55bd8a4c97ae in std::function<void ()>::operator()() const /var/local/ldb-toolchain/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/std_function.h:560:9
#3 0x55bd8a4c97ae in doris::Thread::supervise_thread(void*) /root/doris/be/src/util/thread.cpp:498:5
#4 0x7f7601092608 in start_thread /build/glibc-SzIz7B/glibc-2.31/nptl/pthread_create.c:477:8
#5 0x7f760133f132 in __clone /build/glibc-SzIz7B/glibc-2.31/misc/../sysdeps/unix/sysv/linux/x86_64/clone.S:95
   
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /root/doris/be/src/runtime/fragment_mgr.cpp:1064:20 in
*** Query id: 0-0 ***
*** is nereids: 0 ***
*** tablet id: 0 ***
*** Aborted at 1731663847 (unix time) try "date -d @1731663847" if you are using GNU date ***
*** Current BE git commitID: b663df0e50 ***
*** SIGSEGV address not mapped to object (@0x0) received by PID 17169 (TID 17463 OR 0x7f746d21a700) from PID 0; stack trace: ***
0# doris::signal::(anonymous namespace)::FailureSignalHandler(int, siginfo_t*, void*) at /root/doris/be/src/common/signal_handler.h:421
1# PosixSignals::chained_handler(int, siginfo_t*, void*) [clone .part.0] in /usr/lib/jvm/java-17-openjdk-amd64/lib/server/libjvm.so
2# JVM_handle_linux_signal in /usr/lib/jvm/java-17-openjdk-amd64/lib/server/libjvm.so
3# 0x00007F7601263090 in /lib/x86_64-linux-gnu/libc.so.6
4# doris::FragmentMgr::_check_brpc_available(std::shared_ptr<doris::PBackendService_Stub> const&, doris::FragmentMgr::BrpcItem const&) in /mnt/ssd01/pipline/OpenSourceDoris/clusterEnv/P0/Cluster0/be/lib/doris_be
5# doris::FragmentMgr::cancel_worker() at /root/doris/be/src/runtime/fragment_mgr.cpp:1022
6# doris::Thread::supervise_thread(void*) at /root/doris/be/src/util/thread.cpp:499
7# start_thread at /build/glibc-SzIz7B/glibc-2.31/nptl/pthread_create.c:478
8# __clone at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Related PR: #xxx

Problem Summary:

Release note

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Check List (For Author)

• Test

  • Regression test
  • Unit Test
  • Manual test (add detailed scripts or steps below)
  • No need to test or manual test. Explain why:
    • This is a refactor/code format and no logic has been changed.
    • Previous test can cover this change.
    • No code files have been changed.
    • Other reason

• Behavior changed:

  • No.
  • Yes.

• Does this need documentation?

  • No.
  • Yes.

Check List (For Reviewer who merge this PR)

• Confirm the release note
• Confirm test cases
• Confirm document
• Add branch pick label

[doris-robot]

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Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
3. What features were added. Why was this function added?
4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?

[mrhhsg]

run buildall

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[github-actions]

PR approved by at least one committer and no changes requested.

[github-actions]

PR approved by anyone and no changes requested.

[doris-robot]

TeamCity be ut coverage result:
Function Coverage: 38.00% (9902/26057)
Line Coverage: 29.17% (82708/283521)
Region Coverage: 28.31% (42496/150100)
Branch Coverage: 24.88% (21543/86588)
Coverage Report: http://coverage.selectdb-in.cc/coverage/7dfed67f3fe9b539e3e1c3d4c641a2c9957bf57d_7dfed67f3fe9b539e3e1c3d4c641a2c9957bf57d/report/index.html