Update git submodules

* Update docs/submodules/doctor from branch 'stable/gambia'
  - fix the username to login undercloud in Apex

    Change-Id: I6d5325166db642b3481a0327f518ec821a8ab378
    Signed-off-by: dongwenjuan <dong.wenjuan@zte.com.cn>
    (cherry picked from commit 2a1d82ade82c3076a630af41da493da5a606993d)

diff --git a/docs/submodules/doctor b/docs/submodules/doctor
index bec932d..a7517dd 160000 (submodule)
--- a/docs/submodules/doctor
+++ b/docs/submodules/doctor
@@ -1 +1 @@
-Subproject commit bec932db65949fb4c8356c590efc85eda6845c00
+Subproject commit a7517dda9ede8bedadcbcedf7a46187268977d3a