Assignment Restriction Issue

This commit fixes an issue where we were not checking the restrictions on Ticket assignment correctly. isAccessLimited returns true if showAssignedOnly is true, so we wouldn't want to negate the isAccessLimited check (that would return true if access is not limited).

Also, if an Agent's access is limited to assigned tickets only, we can return the assigned tickets once we have them without needing to go through any further processing.

Finally, we should still allow an agent to view an assigned ticket even if the ticket is closed.

Note: queue counts update themselves a little after you toggle the 'Limit ticket access to ONLY assigned tickets' check box. The 'See all tickets in search results, regardless of access' still works correctly as well.