CBQE-0: added test case to offline/online upgrade from 2.5.1 -> 3.0.0

Change-Id: I65adba42a81a503a6f3fff81290cb17b6c06d7e1
Reviewed-on: http://review.couchbase.org/39230
Reviewed-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>
Tested-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>