qemu-ga: debug printouts to help troubleshoot installation

Debug printouts extended, helps installation troubleshooting

Signed-off-by: Yossi Hindin <yhindin@redhat.com>
Message-Id: <1430913460-13174-3-git-send-email-yhindin@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>