Add test for update role without name

There was no test that showed what happens when a role update is done
without a name. The test shows that when using the LDAP assignment
backend a role update without a name raises an exception.

Change-Id: I9ca7d1af432cec2f0dcc5833e196f5e1e18a8013
Partial-Bug: #1241134
Merge "Add test for update role without name"