test n rollbacks

Sends a stream request with start seqno greater than seqno of vbucket.  Expects
    to receive a rollback response with seqno to roll back to.  Instead of rolling back
    resend stream request n times each with high seqno's and expect rollback for each attempt.

Change-Id: I8a92b860a04593e8e005da2c0de74ca09d547159