use "install_packages" function to install smoketest dependencies
smoketest: remove no longer used "fixed_ips" array
smoketest: try to avoid bash v4 features

SLES does only have a bash-3.2
Merge pull request #262 from dirkmueller/release/roxy/master

Update schema json for schema-revision attribute
Merge pull request #249 from rhafer/feature/roxy-smoketest-on-sles

Smoketests passes merging
Disable COW images for Xen

COW Images are based on QCOW2, which is not supported
by Xen (at least SUSE's version of it).