Made general name validation less strict

1. Made valid_name validation much less strict
2. Changed validation type for cluster, nodegroup and templates to
   new 'valid_name_hostname' that is equal to old "valid_name" validation

Closes-Bug: #1240144

Change-Id: I3048e91f8e179aa5be510feb1c5872b40b6dc3c1
Merge "Made general name validation less strict"