Our dib-lint checking is only considering scripts with #!/bin/bash.
While there's nothing really wrong with some other shebang line like
"#!/usr/bin/env bash" let's keep things consistent.
We can use the same regex match to reduce a few forks in the main
checking.
Also a minor cleanup to the file matching
Change-Id: I609721b2671e704ea26075dad7e5b39a8b858f6b
uses upstream's stage4 images, includes all the needed bells and
whistles for openstack on kvm.
Change-Id: Ibca43173c30c2a74a73a2e2d9dd6d6d832c62694
Closes-Bug: 1530911