Add skip check to 'test_update_volume_attachment'

Check tempest.conf to see if 'swap_volume' is enabled in
'compute-feature-enabled'. If 'swap_volume' is set to False,
then skip 'test_update_volume_attachment'

Change-Id: Ieaf2f035080264d3a78fc0417d421a17e15056d3
1 file changed