Update git submodules

* Update docs/submodules/doctor from branch 'master'
  - Add maintenance test code

      -Add sample admin_tool
      -Add sample app_manager
      -Modify sample inspector

    JIRA: DOCTOR-106

    Change-Id: I52cffecaa88452ce5e7cc6487534c88fcfd378ad
    Signed-off-by: Tomi Juvonen <tomi.juvonen@nokia.com>
  - Add setup and cleanup for maintenance test

    JIRA: DOCTOR-106

    Change-Id: Idb95e1391e8f9094f68e2c7bc79fd2d7e01af9de
    Signed-off-by: Tomi Juvonen <tomi.juvonen@nokia.com>

diff --git a/docs/submodules/doctor b/docs/submodules/doctor
index b2bb504..4639f15 160000 (submodule)
--- a/docs/submodules/doctor
+++ b/docs/submodules/doctor
@@ -1 +1 @@
-Subproject commit b2bb504032ac81a2ed3f404113b097d9ce3d7f14
+Subproject commit 4639f15e6db2f1480b41f6fbfd11d70312d4e421