Skip test_volume_extend_when_volume_has_snapshot until bug 1687044 is fixed

This test is still failing at a really high rate:

http://status.openstack.org/elastic-recheck/#1687044

And that's just the jobs where elastic-recheck didn't time out
waiting to get logs, so the actual failure rate is probably higher.

Let's skip it for now.

Change-Id: I49cfa97c5a2a8d30514adb59d9ad3ae35a6ade37
Related-Bug: #1687044
1 file changed