desktop_login: bit more generous timeout for check_desktop
    
    It can take some time for first login of a user (especially in
    KDE). Test has been failing lately on Rawhide because of this.
    It seems until recently we never got a still screen when trying
    to log in as Jim - so the effective wait for login to complete
    was 60 seconds, 30 seconds for wait_still_screen to time out
    then 30 seconds for the actual login needle assertion - but now
    we are getting a blank screen for 5 seconds which satisfies
    wait_still_screen almost immediately, so effective timeout for
    the login process is only 35 seconds, which isn't long enough.
    So let's bump the check_desktop timeout to 60 seconds.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>