Add qcow2 generation for better test coverage
Add qcow2 generation for better test coverage

Add qcow2 generation for better test coverage.  Add "-x" to the dib
invocations so we can better debug failure cases.

Change-Id: Idd0e33c70fcd7737e6dc43e26b054fbc2982c022

switch-ch/diskimage-builder,switch-ch/diskimage-builder,takahashinobuyuki/diskimage-builder,zioproto/diskimage-builder,takahashinobuyuki/diskimage-builder,openstack/diskimage-builder,zioproto/diskimage-builder,openstack/diskimage-builder