Description of problem:
Administer->Settings, On tab Autentication - Input field for 'Trusted hosts' missing validation on input fields.

Version-Release number of selected component (if applicable):
6.15.0

How reproducible:
Always

Steps to Reproduce:
1. Navigate to Administer -> Settings page, switch to tab 'Authentication'
2. Inside input filed of 'Trusted hosts' give multiple valid input comma separated as per maintained in Description.

Actual results:
The input filed accepts any value in the field and has no validation check on it.

Expected results:
There should be a validation on the type of input `Trusted hosts` should accept like a hostname.

Additional info: