elements: zypper-minimal: Refresh repositories after adding the cache
elements: zypper-minimal: Refresh repositories after adding the cache

The refresh operation must happen after the cache has been added in
order to ensure that whatever is in the cache is still relevant to
the current build and we are not using stale packages.

Change-Id: Iafd718e9738f85b8c235806c027665730f44d89b

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