Comment 4 for bug 1538583

The replicaset is changed as a result of adding a new IP to the API host ports:

2016-01-29 19:33:24 DEBUG juju.state address.go:137 setting API hostPorts: [[52.35.31.97:17070 172.31.22.1:17070 127.0.0.1:17070 [::1]:17070]]
2016-01-29 19:33:24 DEBUG juju.worker.peergrouper desired.go:38 calculating desired peer group
2016-01-29 19:33:24 DEBUG juju.worker.peergrouper desired.go:39 members: map[*peergrouper.machine]*replicaset.Member{&peergrouper.machine{id: "0", wantsVote: true, hostPort: "172.31.22.1:37017"}
:(*replicaset.Member)(0xc820625040)}
2016-01-29 19:33:24 DEBUG juju.worker.peergrouper desired.go:40 extra: []replicaset.Member(nil)
2016-01-29 19:33:24 DEBUG juju.worker.peergrouper desired.go:41 maxId: 1
2016-01-29 19:33:24 DEBUG juju.worker.peergrouper desired.go:110 assessing possible peer group changes:
2016-01-29 19:33:24 DEBUG juju.worker.peergrouper desired.go:116 machine "0" is already voting
2016-01-29 19:33:24 DEBUG juju.worker.peergrouper desired.go:134 assessed
2016-01-29 19:33:24 DEBUG juju.worker.peergrouper worker.go:282 desired peer group members: []replicaset.Member{replicaset.Member{Id:1, Address:"172.31.22.1:37017", Arbiter:(*bool)(nil), BuildIn
dexes:(*bool)(nil), Hidden:(*bool)(nil), Priority:(*float64)(nil), Tags:map[string]string{"juju-machine-id":"0"}, SlaveDelay:(*time.Duration)(nil), Votes:(*int)(nil)}}
2016-01-29 19:33:24 DEBUG juju.replicaset replicaset.go:168 Set() changing replica set
from {Name: juju, Version: 1, Members: {Member{1 "52.35.31.97:37017" map[juju-machine-id:0]}}}
  to {Name: juju, Version: 2, Members: {Member{1 "172.31.22.1:37017" map[juju-machine-id:0]}}}