s390x: basic self test

Test if the general infrastructure is working. The test will fail until
we have proper sclp console output.

Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20170522085702.17856-3-david@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>