JWT token expiration issue

When using external JWT authentication, it fails because the server is using non GMT based expiration, which IMO isn’t right. I hereby propose changing line 62 in JwtAccessToken.php to current_time( ‘timestamp’, 1) which uses correct time rather than local based time.

	public function createAccessToken( $client_id, $user_id, $scope = null, $includeRefreshToken = true ) {
		$expires = current_time( 'timestamp', 1 ) + $this->config['access_lifetime'];
		$id      = $this->generateAccessToken();