Added validation for long hostnames

* Sahara checks that composite instance name with maximum id doesn't
  exceed default limit 64 for characters when changing hostnames by command:
  "hostname new-host-name"
* Composite name described in previous point is:
  "cluster_name" + "node_group_name + "instance_id" + "." + "novalocal"
* Applied for cluster creation validation and scailing operation
* Exctracted constructing of composite name to separate utils method

Change-Id: I2dd3724398c10fb1d6dad87606f6123e50f851d5
Closes-Bug: #1300391
Merge "Added validation for long hostnames"