failover in safe mode lead one shard have two master

[bbqccx]

We have two clusters, each cluster consists of 2 servers, and each server has 8 nodes。 Then we kill one server from each cluster，we find one cluster can lead one node failover， cluster 1 ：msg":"safe mode, loop ratio 0.40, allnodes: 16, failnodes: 7 cluster 2：msg":"safe mode, loop ratio 0.40, allnodes: 16, failnodes: 8

and in cluster 1，when we startup broken server‘s node , we find one shard have two master，and two master have different version。

[bbqccx]

cluster 1 have one node success failover： caller":"failover/cluster.go:197","msg":"Finish the fail over task","task":{