addback after autofailover due to reboot causes rebalance failure

1) setup a 4 node cluster
2) enable autofailover for 30s
3) reboot one of the nodes
4) wait for it to come back, then readd and rebalance.

{{case_clause,
{badrpc,
{'EXIT',
badmatch,{error,ehostunreach,

{gen_server,call, [<0.21127.3>, start_vbucket_filter_change]}

}}}},
[

{ns_vbm_sup,change_vbucket_filter,4}

,

{ns_vbm_sup,'-set_replicas/3-fun-2-',5}

,

{lists,foldl,3}

,

{ns_vbm_sup,set_replicas,3}

,

{ns_vbm_sup,'-set_replicas/2-fun-1-',3}

,

{lists,foreach,2}

,

{ns_janitor,do_cleanup,3}

,

{ns_rebalancer,'-rebalance/3-fun-0-',5}

]}