Properly account for pipefail during cleanup
Properly account for pipefail during cleanup

Due to a bug in how we were running some of our phases we were not
detecting some nonzero exit's. When this is fixed, dib fails early during
cleanup (leaving some resources attatched) due to not propertly
accounting for pipefail.

Change-Id: Icc0b35acbe035cac12a9291e2d07b6c690c3a6ad

switch-ch/diskimage-builder,openstack/diskimage-builder,CSC-IT-Center-for-Science/diskimage-builder,takahashinobuyuki/diskimage-builder,zioproto/diskimage-builder,openstack/diskimage-builder,switch-ch/diskimage-builder,takahashinobuyuki/diskimage-builder,CSC-IT-Center-for-Science/diskimage-builder,zioproto/diskimage-builder