failed delta recovery followed by failover+rebalance might eject the node while leaving it in vbucket maps

Steps:

1. failover a node
2. attempt delta recovery; if delta recovery fails after updating bucket configs but before bucket are loaded in memcached, that will leave the node marked for delta recovery
3. failover the node again; this drops recovery type to none and marks node as inactiveFailed
4. rebalance; in the very beginning of the rebalance the node will get ejected (since it's marked as failed over); but it will continue to be referenced in vbucket maps, so rebalance will attempt changing replications on this node, which will fail