Array values in settings UI are not displayed correctly after update
Array values in Foreman's settings UI are not rendered correctly after update.
The updated value saves ok but it is displayed without wrapping brackets. This causes failure on next update attempt. One either has to reload the page to get correct value again or write the brackets manually.
Steps to Reproduce:
1. In foreman go to More > Settings > Puppet
2. Choose any of the fields with array, click it to update, press enter to confirm, wait until it gets saved
3. Value is rendered without wrapping 
4. Another attempt to update causes "Value must be an array" error
Should always render arrays in [a, b, c] format.