fix(eslint): Add max-depth rule

.eslintrc.js

                 'beforeLineComment': true
             }
         ],
+        'max-depth': 2,
         'max-len': [ 'error', 80 ],
         'max-lines': 0,
         'max-nested-callbacks': 2,

modules/RTC/TraceablePeerConnection.js

                     // Note that group.semantics is already present
 
                     group.ssrcs = groupSSRCs;
+
+                    // eslint-disable-next-line max-depth
                     if (!groupsMap.has(primarySSRC)) {
                         groupsMap.set(primarySSRC, []);
                     }

modules/xmpp/SDP.js

 
                 if (afmtpline) {
                     tmp = SDPUtil.parseFmtp(afmtpline);
+
+                    // eslint-disable-next-line max-depth
                     for (k = 0; k < tmp.length; k++) {
                         elem.c('parameter', tmp[k]).up();
                     }
                     // FIXME what is this ? global APP.RTC in SDP ?
                     const localTrack = APP.RTC.getLocalTracks(mline.media);
 
+                    // eslint-disable-next-line max-depth
                     if (localTrack) {
                         // FIXME before this changes the track id was accessed,
                         // but msid stands for the stream id, makes no sense ?
                         msid = localTrack.getTrackId();
                     }
+
+                    // eslint-disable-next-line max-depth
                     if (msid !== null) {
                         msid = SDPUtil.filterSpecialChars(msid);
                         elem.c('parameter');
                         uri: tmp.uri,
                         id: tmp.value
                     });
+
+                    // eslint-disable-next-line max-depth
                     if (tmp.hasOwnProperty('direction')) {
+
+                        // eslint-disable-next-line max-depth
                         switch (tmp.direction) {
                         case 'sendonly':
                             elem.attrs({ senders: 'responder' });

modules/xmpp/SdpConsistency.js

                         const primarySsrc = parsePrimarySSRC(group);
                         const rtxSsrc = parseSecondarySSRC(group);
 
+                        // eslint-disable-next-line max-depth
                         if (primarySsrc === newPrimarySsrc) {
                             group.ssrcs
                                 = `${this.cachedPrimarySsrc} ${rtxSsrc}`;