Refactored indices aliases api to make use of the new ack mechanism

[javanna]

Refactored indices aliases api to make use of the new recently introduced generic ack mechanism

Closes #4114

[kimchy]

Looks good. Note that by removing the node aliases action, it means that if we back port it to 0.90, then failures will happen between different version nodes (on aliases API) until the cluster is on the same version.

[javanna]

I had a deeper look at this and figured out that it shouldn't be a problem.

If an updated master receives a cluster/nodeAliasesUpdated request (the old format of ack for aliases) there's no endpoint registered for it, then it will return an exception (ActionNotFoundTransportException). But the sender node won't do anything with it as it uses an EmptyTransportResponseHandler. As a result the only downside, which doesn't hurt, is a warning in the master log:

Message not fully read (request) for [*] and action [cluster/nodeAliasesUpdated], resetting

The other way around, if an updated node doesn't send back the old format of ack request, an older version master will just timeout and return acknowledged:false.

I think it's fine in case of rolling upgrade, will merge this and backport it to 0.90 too.

[javanna]

Merged via b2ad34c and backported to 0.90.