feat(xmpp) drop the useStunTurn option

Always attempt to discover the configured STUN/TURN servers.

doc/API.md

             - domain
             - muc
             - anonymousdomain
-        4. useStunTurn -
-        5. enableLipSync - (optional) boolean property which enables the lipsync feature. Currently works only in Chrome and is disabled by default.
+        4. enableLipSync - (optional) boolean property which enables the lipsync feature. Currently works only in Chrome and is disabled by default.
 
 2. connect(options) - establish server connection
     - options - JS Object with ```id``` and ```password``` properties.

modules/xmpp/strophe.jingle.js

                     iceservers[j] = temp;
                 }
 
-                if (options.useStunTurn) {
-                    let filter;
-
-                    if (options.useTurnUdp) {
-                        filter = s => s.urls.startsWith('turn');
-                    } else {
-                        // By default we filter out STUN and TURN/UDP and leave only TURN/TCP.
-                        filter = s => s.urls.startsWith('turn') && (s.urls.indexOf('transport=tcp') >= 0);
-                    }
-
-                    this.jvbIceConfig.iceServers = iceservers.filter(filter);
-                }
+                let filter;
 
-                if (options.p2p && options.p2p.useStunTurn) {
-                    this.p2pIceConfig.iceServers = iceservers;
+                if (options.useTurnUdp) {
+                    filter = s => s.urls.startsWith('turn');
+                } else {
+                    // By default we filter out STUN and TURN/UDP and leave only TURN/TCP.
+                    filter = s => s.urls.startsWith('turn') && (s.urls.indexOf('transport=tcp') >= 0);
                 }
 
+                this.jvbIceConfig.iceServers = iceservers.filter(filter);
+                this.p2pIceConfig.iceServers = iceservers;
             }, err => {
                 logger.warn('getting turn credentials failed', err);
                 logger.warn('is mod_turncredentials or similar installed?');

modules/xmpp/xmpp.js

             now);
 
         this.eventEmitter.emit(XMPPEvents.CONNECTION_STATUS_CHANGED, credentials, status, msg);
-        if (status === Strophe.Status.CONNECTED
-            || status === Strophe.Status.ATTACHED) {
-            if (this.options.useStunTurn
-                || (this.options.p2p && this.options.p2p.useStunTurn)) {
-                this.connection.jingle.getStunAndTurnCredentials();
-            }
+        if (status === Strophe.Status.CONNECTED || status === Strophe.Status.ATTACHED) {
+            this.connection.jingle.getStunAndTurnCredentials();
 
             logger.info(`My Jabber ID: ${this.connection.jid}`);