Update git submodules

* Update docs/submodules/doctor from branch 'stable/euphrates'
  - Fix defaultbranch in .gitreview

    Change-Id: Ia02f17d52b5d3ef836567d60bf541513b0419977
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>

diff --git a/docs/submodules/doctor b/docs/submodules/doctor
index 55ad897..50e5435 160000 (submodule)
--- a/docs/submodules/doctor
+++ b/docs/submodules/doctor
@@ -1 +1 @@
-Subproject commit 55ad897310d1258679911acce80fd4bb878d9fef
+Subproject commit 50e54357973864dcc516e693181f4a5a881cec17