Run attach/detach volume tests even without ssh

When validation it's turned off, it is still possible to run the
attach/detach volume tests. They will test less, but still be
valuable.

Tests modified:
- test_attach_detach_volume
- test_attach_volume_shelved_or_offload_server
- test_detach_volume_shelved_or_offload_server

Not having them running in the gate allowed for bug/1600186 to
slipt through.

Closes-Bug: 1600191
Change-Id: Ia60fa810790f2d3b57dfd73104e7522f72d837b4
1 file changed