Fixed RunOnMainThread.Run() in batch mode.

EditorApplication.update isn't called in batch mode which results in
all deferred jobs never executing.  This changes RunOnMainThread.Run() to
always run a job immediately in batch mode.

Change-Id: I9173c412131851aff5053e4f1b70ad816a6d2a17

Author: Stewart Miles

source/VersionHandlerImpl/src/RunOnMainThread.cs

@@ -359,7 +359,7 @@ public static void Run(Action job, bool runNow = true) {
         // as part of the process until the queue is empty.
         // If we're not executing the job right now, the job queue is pumped from the UnityEditor
         // update event.
-        if ((firstJob || ExecuteNow) && runNow && OnMainThread) {
+        if (firstJob && (runNow || ExecuteNow) && OnMainThread) {
             ExecuteAll();
         }
     }