CBD-1438: Clean up RPMs from previous builds

Change-Id: I4c5f784a53c7c3197d81fbbdc360536c2dad5013
Reviewed-on: http://review.couchbase.org/42380
Reviewed-by: Chris Hillery <ceej@couchbase.com>
Tested-by: Chris Hillery <ceej@couchbase.com>