MB-11563 Add a unit test case for rollback after adding partitions

Change-Id: I2bea97b64f99a03d5d3f369c0d0ad30323227856
Reviewed-on: http://review.couchbase.org/38930
Reviewed-by: Sarath Lakshman <sarath@couchbase.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: buildbot <build@couchbase.com>