IDEA-107291 "Unshelve" into a new changelist puts new files into active changelist for HG

*CheckinEnvironment.scheduleUnversionedFilesForAddition method is async for hg, so HgVcs.fileListenerIsSynchronous should return false.

plugins/hg4idea/src/org/zmlx/hg4idea/HgVcs.java

@@ -188,6 +188,11 @@ public class HgVcs extends AbstractVcs<CommittedChangeList> {
     return null;
   }
 
+  @Override
+  public boolean fileListenerIsSynchronous() {
+    return false;
+  }
+
   @Override
   public CommittedChangesProvider getCommittedChangesProvider() {
     return commitedChangesProvider;