Fix reaction overlay not showing on first try in RTL mode.

The view needs to request a call to `fitsSystemWindows`; otherwise it
cannot determine where to layout itself within the parent that uses
fitsSystemWindows method to determine the boundary of it.

This fixes the issue reported in [the beta 5.3 forum](https://community.signalusers.org/t/beta-feedback-for-the-upcoming-android-5-3-release/25088/315).

app/src/main/java/org/thoughtcrime/securesms/conversation/ConversationReactionDelegate.java

@@ -115,6 +115,7 @@ final class ConversationReactionDelegate {
 
   private @NonNull ConversationReactionOverlay resolveOverlay() {
     ConversationReactionOverlay overlay = overlayStub.get();
+    overlay.requestFitSystemWindows();
 
     overlay.setListVerticalTranslation(translationY);
     overlay.setOnHideListener(onHideListener);