rebalance failing with retry_not_ready_vbuckets error if ns_server janitors sets the vbucket state from pending to dead when rebalance fails or stops

when rebalance fails or is stopped by the user the vbucket state for those rebalance operations which were making progress are still pending.
ns_server janitor runs every few seconds which will change the vbucket state from pending->dead

now when the user restarts the rebalance sooner than 5 minutes ep-engine will try to reuse that tap stream and will not send TAP_VBUCKET_SET when restarting the takeover and since the vbucket state is dead now ep-engine will not start the vbucket transfer and this will result in rebalance getting stuck.