Stress action for volume attach verify

The new stress action is able to verify the volume attachment,
on the guest.

The ``new_volume`` option can help in finding out the issue is on the
nova side (or on things controlled by nova) or on cider side.

Change-Id: I2d4c8548a2617dd33e2f116fce8b0b3d379b808e
Merge "Stress action for volume attach verify"