JCBC-27: exponential backoff when cluster is not warmed up

This changeset prevents operations against a warming up cluster and
waits until its in a warmed-up state or throws an exception after
the backoff limit is reached.

Change-Id: I655700909b98179c3f828df863c2a4ce355fc9fe
Reviewed-on: http://review.couchbase.org/22933
Reviewed-by: Matt Ingenthron <matt@couchbase.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>