previously, as long as user has ReassignTicket, RT::Ticket::CurrentUserCanSetOwner
would return true for both "Take" and "Steal" types no matter what the ticket's
current owner is, which is not good, as we want to use it like(in /Elements/Tabs):

    my ($can_take, $msg) = $ticket->CurrentUserCanSetOwner( Type => 'Take' );
    if ( $can_take ) {
        # show "Take" link
    }

this commit merges the logic of "check ticket's current owner too" for Take/Steal
into RT::Ticket::CurrentUserCanSetOwner.

see also #28211