Correct RE that validates vCenter cluster names

- match cluster names that include metachars (!@#$%^&*()_+{}:"<>?)
  e.g. 'cluster No.42'
- right now cluster names with comma are not supported
- adjust message a little, while here

Change-Id: Ic36e70ff0d0bc7bd3d23ce9cc633cec6a18df581
Closes-Bug: 1340886
Merge "Correct RE that validates vCenter cluster names"