Update git submodules

* Update docs/submodules/doctor from branch 'master'
  - 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>

diff --git a/docs/submodules/doctor b/docs/submodules/doctor
index 54b4b34..a321477 160000 (submodule)
--- a/docs/submodules/doctor
+++ b/docs/submodules/doctor
@@ -1 +1 @@
-Subproject commit 54b4b3418aae6d649411b531f0aa8bc4d9fd6b2c
+Subproject commit a321477d00ccb84b0d99e7476e4306605498409d