Update git submodules

Update git submodules

* Update docs/submodules/doctor from branch 'master'
  - Merge "bugfix: kill the stunnel when cleanup"
  - bugfix: kill the stunnel when cleanup

    Popen.terminate() will kill the child process, but if you set the
    shell argument to True, this is the process ID of the spawned shell,
    so the stunnels are still exit.It will cause the failure of stunnel
    setup in the next test runtime.

    see: https://stackoverflow.com/questions/4789837/how-to-terminate-a-python-subprocess-launched-with-shell-true/4791612#4791612

    Change-Id: I578611510f5bd1eb0dbd9a08ab408ccf101594f7
    Signed-off-by: dongwenjuan <dong.wenjuan@zte.com.cn>