CBLT-283:  fix up parsing of build revision

Change-Id: I043215d3201cfdf9cd4313a0a1c2aa0329e19c85
Reviewed-on: http://review.couchbase.org/36768
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>