ipatests: kinit on server for test_proxycommand_invalid_shell
    
    We've seen some intermittent failures of this test with warnings
    about passwords about to expire. We suspect there may be a time
    difference between the client and server so set the passwords
    on the server instead to be sure that time is correct.
    
    https://pagure.io/freeipa/issue/8785
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>