client/v3: clear auth token when encounter ErrInvalidAuthToken

Old etcdserver which have not apply pr of etcd-io#12165 will check auth token
even if the request is a Authenticate request.

If the client has a invalid auth token, it will not able to update it's
token, since the Authenticate has a invalid auth token.

This fix clear the auth token when encounter an ErrInvalidAuthToken to
talk with old version etcd servers.

Fix etcd-io#12385 with etcd-io#12165 and etcd-io#12264

client/v3/retry_interceptor.go

@@ -74,6 +74,12 @@ func (c *Client) unaryClientInterceptor(logger *zap.Logger, optFuncs ...retryOpt
 				continue
 			}
 			if callOpts.retryAuth && rpctypes.Error(lastErr) == rpctypes.ErrInvalidAuthToken {
+				// clear auth token befault refreshing it.
+				// call c.Auth.Authenticate with an invalid token will always fail the auth check on the server-side,
+				// if the server has not apply the patch of pr #12165 (https://github.com/etcd-io/etcd/pull/12165)
+				// and a rpctypes.ErrInvalidAuthToken will recursively call c.getToken until system run out of resource.
+				c.authTokenBundle.UpdateAuthToken("")
+
 				gterr := c.getToken(ctx)
 				if gterr != nil {
 					logger.Warn(