MT#56085 Reply with 486 from WebRTC when the user is busy in another conversation

Change-Id: I3eea53440fe14452e0abe8d873f6ac99961e45f6
(cherry picked from commit 175c344157)

src/api/ngcp-call.js

@@ -134,6 +134,12 @@ export function callRegister ({ instanceId }) {
         delegateEvent('registrationFailed')
         $userAgent.on('newRTCSession', (event) => {
             if (event.originator === 'remote') {
+                if ($incomingRtcSession || $outgoingRtcSession) {
+                    event.session.terminate({
+                        status_code: 486,
+                        reason_phrase: 'Busy'
+                    })
+                } else {
                     $incomingRtcSession = event.session
                     $incomingRtcSession.on('peerconnection', () => {
                         $incomingRtcSession.connection.ontrack = handleRemoteMediaStream
@@ -147,6 +153,7 @@ export function callRegister ({ instanceId }) {
                     })
                     callEvent.emit('incoming', $incomingRtcSession)
                 }
+            }
         })
         $userAgent.start()
     }

src/store/call/actions.js

@@ -77,6 +77,7 @@ export default {
             context.commit('hangUpCall')
         } else if (options.cause && !errorVisibilityTimer) {
             context.commit('endCall', options.cause)
+            if (options.cause !== 'Busy') {
                 errorVisibilityTimer = setTimeout(() => {
                     if (context.state.callState === 'ended') {
                         context.commit('hangUpCall')
@@ -84,6 +85,7 @@ export default {
                     errorVisibilityTimer = null
                 }, errorVisibilityTimeout)
             }
+        }
     },
     sendDTMF (context, tone) {
         callSendDTMF(tone)