Log warning instead of error for audio output device change errors

modules/RTC/JitsiTrack.js

@@ -334,7 +334,9 @@ JitsiTrack.prototype.setAudioOutput = function (audioOutputDeviceId) {
     return Promise.all(this.containers.map(function(element) {
         return element.setSinkId(audioOutputDeviceId)
             .catch(function (error) {
-                logger.error('Failed to change audio output device on element',
+                logger.warn(
+                    'Failed to change audio output device on element. Default' +
+                    ' or previously set audio output device will be used.',
                     element, error);
                 throw error;
             });

modules/RTC/RTCUtils.js

@@ -570,7 +570,9 @@ function wrapAttachMediaStream(origAttachMediaStream) {
                 .catch(function (ex) {
                     GlobalOnErrorHandler.callUnhandledRejectionHandler(
                         {promise: this, reason: ex});
-                    logger.error('Failed to set audio output on element',
+                    logger.warn('Failed to set audio output device for the ' +
+                        'element. Default audio output device will be used ' +
+                        'instead',
                         element, ex);
                 });
         }