Description of problem:
On cloning an user role, builtin parameter is set to null, causing the role to be treat as 'builtin' (unable to remove it) despite the fact, that API reports builtin: no

Version-Release number of selected component (if applicable):
6.2.0 beta GA17.0

How reproducible:
always

Steps to Reproduce:
1. navigate to Administer -> Roles
2. choose/create one of the roles which are not set as 'builtin' (in UI they are clickable)
3. clone them

Actual results:
Newly created role displayed as builtin despite the fact that `hammer role info` reports on it as 'builtin: no'.

listing the roles using API (curl -k https://<sat6>/api/v2/roles) shows, that the 'builtin' parameter is set to null.

Expected results:
'builtin' parameter defaults to 'false'