MRE timeouts will affect other objects in scene

[stephenc87]

If there is an issue loading elements inside an MRE then other objects will affected and may not instantiate inside scene
Was able to reproduce this issue inside a TestBed, used an MRE I found online "ws://piano.norybiak.com" and duplicated 8 MicroAppRoot objects pointing to the server

Loading the Piano once will store it in cache and scene will continue to instantiate other objects on failure
Clearing cache may be necessary for reproducing error

Logs will fill with Timeout errors, and other objects will fail to be instantiated in to the scene in an unreliable manner

Here is a preview of the last error message, others are fairly similar

TimeoutException: Failed to acquire exclusive loading rights for http://piano.norybiak.com/notes/108.ogg
MixedRealityExtension.Assets.AssetFetcher`1+d__1[T].MoveNext () (at <16e38f6fcabd4ab4a3262f081b6e2453>:0)
--- End of stack trace from previous location where exception was thrown ---
System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () (at :0)
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) (at :0)
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) (at :0)
System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) (at :0)
System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult () (at :0)
MixedRealityExtension.Assets.AssetLoader+d__13.MoveNext () (at <16e38f6fcabd4ab4a3262f081b6e2453>:0)
--- End of stack trace from previous location where exception was thrown ---
System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () (at :0)
System.Runtime.CompilerServices.AsyncMethodBuilderCore+<>c.b__6_0 (System.Object state) (at :0)
UnityEngine.UnitySynchronizationContext+WorkRequest.Invoke () (at :0)
UnityEngine.UnitySynchronizationContext:ExecuteTasks()

[stephenc87]

Changing
private void StartApp() { Debug.Log("Starting MRE app."); MREComponent?.EnableApp() _running = true; }
to
private async void StartApp() { Debug.Log("Starting MRE app."); await MREComponent?.EnableApp() _running = true; }
in LaunchMRE.cs appears to help resolve the issue