Update git submodules

* Update docs/submodules/releng from branch 'master'
  - Merge "[Dovetail] Increase frequency of Dovetail runs on Apex"
  - [Dovetail] Increase frequency of Dovetail runs on Apex

    Run Dovetail tests on every deployment of os-nosdn-nofeature to improve
    testing turn-around time as we are approaching the next release of
    Dovetail.

    Change-Id: Ie4baf3c2f607aaf09135c4021258e9afb0aec826
    Signed-off-by: Georg Kunz <georg.kunz@ericsson.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 6dd3fcc..c31bf10 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 6dd3fcc928d7540c9d725b0bd8b3c72b863eb819
+Subproject commit c31bf107ee40aa74582ffdbfa1d868e3b0b708e4