In preparation for promoting the openSUSE jobs to voting ones we should
use the OpenStack mirrors. As such, the opensuse elements are modified
to make use of the DIB_DISTRIBUTION_MIRROR variable which is normally
exported by the openstack-ci-mirrors element.
Change-Id: Ie588c1c1eec13190cfb2ec718ba51f8c9878283f
Currently openSUSE 42.3 has entered feature freeze mode
so it is a good point in time to verify that 42.3 builds
are working successfully. Also test opensuse-minimal for
platforms that support it (need working zypper package)
Change-Id: I4c613e1e68cb7375c29d544bbf70b5da9bf21414
