read and parse os_release on openSUSE

Signed-off-by: Michal Toman <mtoman@redhat.com>
Signed-off-by: Jiri Moskovcak <jmoskovc@redhat.com>
add test for parse_release + openSUSE

Signed-off-by: Michal Toman <mtoman@redhat.com>
Signed-off-by: Jiri Moskovcak <jmoskovc@redhat.com>