Update git submodules
* Update docs/submodules/releng from branch 'master'
- Fix Manual Triggering of Docker Jobs
When manually triggering a docker job (or even through timed builds),
GERRIT_EVENT_TYPE will not get set. This does gets set when the job is
triggered by a Gerrit event (ex: ref-updated, comment-added).
Specifying the variable lookup to default to nothing (ex: "${FOO:-}")
should allow non-Gerrit triggered jobs to complete successfully.
Change-Id: Ic1ba8ebef0967b0f20a2d6385ce0e0b4876901dc
Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>