[RN] CONFERENCE_FAILED error message in redux

In order to support XMPP authentication, we'll need the message
accompanying the error and carried by lib-jitsi-meet's
CONFERENCE_FAILED in the redux store. We already carry the message in
the redux action and we've got the error in the redux store.

react/features/base/connection/actions.native.js

          * Rejects external promise when connection fails.
          *
          * @param {JitsiConnectionErrors} err - Connection error.
+         * @param {string} msg - Error message supplied by lib-jitsi-meet.
          * @returns {void}
          * @private
          */
-        function _onConnectionFailed(err) {
+        function _onConnectionFailed(err, msg) {
             unsubscribe();
-            console.error('CONNECTION FAILED:', err);
-            dispatch(connectionFailed(connection, err));
+            console.error('CONNECTION FAILED:', err, msg);
+            dispatch(connectionFailed(connection, err, msg));
         }
 
         /**

react/features/base/connection/reducer.js

 /* @flow */
 
-import { assign, ReducerRegistry, set } from '../redux';
+import { assign, ReducerRegistry } from '../redux';
 import { parseURIString } from '../util';
 
 import {
         { connection }: { connection: Object }) {
     return assign(state, {
         connecting: undefined,
-        connection
+        connection,
+        error: undefined,
+        errorMessage: undefined
     });
 }
 
  */
 function _connectionFailed(
         state: Object,
-        { connection }: { connection: Object }) {
+        { connection, error, message }: {
+            connection: Object,
+            error: string,
+            message: ?string
+        }) {
     if (state.connection && state.connection !== connection) {
         return state;
     }
 
     return assign(state, {
         connecting: undefined,
-        connection: undefined
+        connection: undefined,
+        error,
+        errorMessage: message
     });
 }
 
 function _connectionWillConnect(
         state: Object,
         { connection }: { connection: Object }) {
-    return set(state, 'connecting', connection);
+    return assign(state, {
+        connecting: connection,
+        error: undefined,
+        errorMessage: undefined
+    });
 }
 
 /**