added xdcr upgrade test from 2.5.0

Change-Id: I23096a249b13d1010ccb39acdb8909bfab933393
Reviewed-on: http://review.couchbase.org/34121
Reviewed-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>
Tested-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>