Graph crash at exit

[SuperYoko]

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Describe the bug (required)

nebula-graphd will crash at exit at master.

Your Environments (required)

• OS: uname -a
Linux host211-cluster 3.10.0-1160.45.1.el7.x86_64 #1 SMP Wed Oct 13 17:20:51 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
• Compiler: g++ --version or clang++ --version
  (VEsoft Inc. Build) clang version 10.0.0
  Target: x86_64-vesoft-linux
  Thread model: posix
• CPU: lscpu
• Commit id: 6849383

How To Reproduce(required)

Steps to reproduce the behavior:

1. Start nebula: nebula.service start all
2. Wait a few seconds and stop nebula, nebula.service stop all

Expected behavior

Additional context