We should test dev branches against dev branches only by default.
At some point we should automate the merges from release->stable->dev
and/or decide how to handle possible conflicts.

This is good enough for the time being.

Change-Id: I70b0244db87bd4a7023004bf50629bb790d6dfc2
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>