Coredump in c++ client

## Bug Report

小爱服务 yuyongrong 报告 coredump，有可能是Pegasus Cilent引起的。

Please answer these questions before submitting your issue. Thanks!

1. What did you do?
If possible, provide a recipe for reproducing the error.

2. What did you expect to see?

3. What did you see instead?
coredump
```
(gdb) bt
#0 0x00007f86b8e3d1d7 in raise () from /lib64/libc.so.6
#1 0x00007f86b8e3e8c8 in abort () from /lib64/libc.so.6
#2 0x00007f86ba2dfa95 in __gnu_cxx::__verbose_terminate_handler ()
at /home/qinzuoyan/git.xiaomi/pegasus/toolchain/objdir/../gcc-4.8.2/libstdc++-v3/libsupc++/vterminate.cc:95
#3 0x00007f86ba2ddc06 in __cxxabiv1::__terminate (handler=)
at /home/qinzuoyan/git.xiaomi/pegasus/toolchain/objdir/../gcc-4.8.2/libstdc++-v3/libsupc++/eh_terminate.cc:38
#4 0x00007f86ba2ddc33 in std::terminate () at /home/qinzuoyan/git.xiaomi/pegasus/toolchain/objdir/../gcc-4.8.2/libstdc++-v3/libsupc++/eh_terminate.cc:48
#5 0x00007f86ba334695 in std::(anonymous namespace)::execute_native_thread_routine (__p=)
at /home/qinzuoyan/git.xiaomi/pegasus/toolchain/objdir/../gcc-4.8.2/libstdc++-v3/src/c++11/thread.cc:92
#6 0x00007f86b91d0dc5 in start_thread () from /lib64/libpthread.so.0
#7 0x00007f86b8eff73d in clone () from /lib64/libc.so.6
```

4. What version of Pegasus are you using?
1.5.6

No project source file, test, reproduction recipe, or specific client entry point is named. Start by examining the supplied gdb backtrace and reproducing the coredump with Pegasus 1.5.6; done means identifying the client failure and adding a regression test that prevents it.

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