Not safe approach for etcd initial-cluster-state

[TeddyAndrieux]

Component:

'salt'

What happened:

In our salt states to deploy etcd we set initial-cluster-state to new if we get an empty member list from pillar, that approach may create a initial-cluster-state new for a new node deployment if for what ever reason we are not able to retrieve the list of etcd member.

initial comment #2099 (comment)

What was expected:

initial-cluster-state should be set to new only for the first etcd node (likely the bootstrap one)

Resolution proposal (optional):

TBD:
Suggestion: this value should be existing by default and we force to new only in the bootstrap script (also make the state raise an error if state=existing and we have empty etcd member list)