CBQE-1902: CBRecoveryTask with wait_completed param

Change-Id: I6a63c9cc61685ed6a39c39ff9f5e59ed1e6fed3a
Reviewed-on: http://review.couchbase.org/33288
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>