CBQE-1902: add async_cbrecovery and cbrecovery in cluster.py

Change-Id: I2f7f2013245c34143bc7468ec861017777987260
Reviewed-on: http://review.couchbase.org/33242
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>