disk_custom_resize_lvm: add some waits
    
    On ppc64le it looks like this test is often failing because it
    takes a second or two to update the partition list after we
    click update settings, but we're not waiting for that, so we
    wind up clicking in the wrong place because we match the next
    partition needle before the list is refreshed but click after
    it's refreshed. Let's hope these waits solve it.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>