Code review comment for lp:~axwalk/juju-core/lp1271504-ensureavailability-agentalive

Reviewers: mp+215172_code.launchpad.net,

Message:
Please take a look.

Description:
state: (demote)promote (un)available state servers

When EnsureAvailability is called, we now check the
availability of existing state servers. If a state server
is unavailable, then we either set WantsVote=false, or
remove it entirely if it doesn't want a vote.

If we need to create new state servers, we will first
promote existing, available, non-voting state servers
before creating new ones.

Availability is currently defined by the state.Machine's
agent presence. We may want to extend this later to also
consider the associated mongo's replicaset member health.

https://code.launchpad.net/~axwalk/juju-core/lp1271504-ensureavailability-agentalive/+merge/215172

(do not edit description out of merge proposal)

Please review this at https://codereview.appspot.com/86490043/

Affected files (+272, -61 lines):
   A [revision details]
   M cmd/juju/ensureavailability_test.go
   M state/addmachine.go
   M state/apiserver/client/client_test.go
   M state/export_test.go
   M state/state_test.go