Update git submodules

Update git submodules

* Update docs/submodules/doctor from branch 'stable/euphrates'
  - Merge "fix collectd's bug" into stable/euphrates
  - fix collectd's bug

    After we move files under doctor_tests and install doctor package,
    the tests/lib/monitors/collectd/collectd_plugin.py file will not be
    in the doctor_tests package.

    Change-Id: I24a098e26ea3cd257f2376458d5c31ecc87aac68
    Signed-off-by: dongwenjuan <dong.wenjuan@zte.com.cn>
    (cherry picked from commit a321477d00ccb84b0d99e7476e4306605498409d)