MB-10422: Failover node will also cause REST failure

Other than URL, user/password, wrong node status can also
cause REST request to fail, such as failover node.

Change-Id: If55da076743c0c30b611358506120ed2c5bdd2ad
Reviewed-on: http://review.couchbase.org/35984
Reviewed-by: Bin Cui <bin.cui@gmail.com>
Tested-by: Bin Cui <bin.cui@gmail.com>