CBIT-847: Re-enable and update trivial rebase detection script

Change-Id: I5183c94d82b795fb30d692dc142f6af5d8034502
Reviewed-on: http://review.couchbase.org/34670
Reviewed-by: Chris Hillery <ceej@couchbase.com>
Tested-by: Chris Hillery <ceej@couchbase.com>