CBLT-301:  differentiate PKGSTORE source from destination

Change-Id: Id9ebf5386902596c989afab2223a45c99ffac0a8
Reviewed-on: http://review.couchbase.org/37508
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>