Optimize the jjb-deploy trigger regex

Optimize the jjb-deploy trigger regex to trigger the job _only_
when the Gerrit CR comment is intended as a command.

The `jjb-deploy` job presently gets triggered and is waste of infra
resources when the keyword is intended as comment in Gerrit.

Ref: https://git.opendaylight.org/gerrit/#/c/80358/

Issue: RELENG-1847
Change-Id: I3b35adb1284d3d9029ba025bf660b66fbb5d98e0
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>