Allow passing extra args to JobExecutionsManager.create()

Java job types require additional parameters beyond cluster_id and
configs.  Add an optional dictionary and an update call to allow
for additional key/value settings.

Closes-Bug: #1268695

Change-Id: I995e648a939063170d1a2ac7040493351fb67f74
Merge "Allow passing extra args to JobExecutionsManager.create()"