[RN] Fix loading config from non-default domains

When a conference is to happen in a domain which is not the defaut, its config
is loaded and set. As part of this process, lib-jitsi-meet is disposed. Because
disposing is asynchronous, events happen in this sequence:

- set new config
- dispose lib (which effectively wipes the config)
- init lib

This results in the library to be initialized without the loaded config, which
was lost. This commit fixes that by delaying setting the config and
re-initializing the library until it was disposed.

react/features/base/lib-jitsi-meet/middleware.js

     const disposeLibPromise
         = initialized ? dispatch(disposeLib()) : Promise.resolve();
 
-    // Let the new config into the Redux store (because initLib will read it
-    // from there).
-    const nextState = next(action);
-
-    disposeLibPromise.then(dispatch(initLib()));
+    disposeLibPromise.then(() => {
+        // Let the new config into the Redux store (because initLib will read it
+        // from there).
+        next(action);
 
-    return nextState;
+        dispatch(initLib());
+    });
 }