CBQE-2033: add UI tests for delta recovery

Change-Id: I1146b6975dc2a46abc8f1842c498ad3b3cd08286
Reviewed-on: http://review.couchbase.org/35040
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>