Unskip test_stamp_pattern

test_stamp_pattern had issues before because the test attached volumes
in VM state when it does not detects hotplug events.

This change have the test to ssh the machine first,
alternativly a pci rescan could be forced.

Notes:
https://docs.google.com/presentation/d/1Im-iYVzroKwXKP23p12Q5vsUGdk2V26SPpLWF3I5dbA/edit#slide=id.p

Closes-bug: #1664793
Change-Id: Iaff1e01dd7ffab238ec73668ae4eee0683f70ffd
1 file changed