СBQE-1119: testBucketModification added

Change-Id: I8abf974db87bd143288f6c200dc1d99bd0c3660a
Reviewed-on: http://review.couchbase.org/27244
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>