qga: Give more --version information

Include the package version information (useful for detecting
builds from git or downstream backports), and the copyright notice.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <20170803163353.19558-4-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>