Remove XDCR env variables from the make simple-test

Change-Id: Icefadb81ec4b693996e5a2acb2e86e80a87b8282
Reviewed-on: http://review.couchbase.org/28323
Tested-by: Ketaki Gangal <ketakigangal@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>