client: Update for go-tpm breaking changes

PolicySecret now returns three values (google/go-tpm#237)

We never read the encoded value from Certify, so we are not affected by:
google/go-tpm#235

Signed-off-by: Joe Richey <joerichey@google.com>

client/session.go

@@ -68,7 +68,7 @@ func newEKSession(rw io.ReadWriter) (session, error) {
 
 func (e ekSession) Auth() (auth tpm2.AuthCommand, err error) {
 	nullAuth := tpm2.AuthCommand{Session: tpm2.HandlePasswordSession, Attributes: tpm2.AttrContinueSession}
-	if _, err = tpm2.PolicySecret(e.rw, tpm2.HandleEndorsement, nullAuth, e.session, nil, nil, nil, 0); err != nil {
+	if _, _, err = tpm2.PolicySecret(e.rw, tpm2.HandleEndorsement, nullAuth, e.session, nil, nil, nil, 0); err != nil {
 		return
 	}
 	return tpm2.AuthCommand{Session: e.session, Attributes: tpm2.AttrContinueSession}, nil