Added silent start option

When the Silent Start Mode is enabled there
will be no 'build started' messages sent back
to Gerrit.

Change-Id: I6bdfa62bc24bac71909638b93ae62ad1c877486e
Merge "Added silent start option" into internal
Added silent start option

When the Silent Start Mode is enabled there
will be no 'build started' messages sent back
to Gerrit.

Change-Id: I6bdfa62bc24bac71909638b93ae62ad1c877486e
Merge branch i