Remove unnecessary PROVIDER_CHANGED broadcast on launch

When the calendar provider process launches, removeStaleAccounts() is
called. This would cause a PROVIDER_CHANGED broadcast regardless of
whether any changes were made or not -- starting all receivers of that
action for no good reason.

Let's only do the broadcast when something actually changed.

Bug: 32997676
Change-Id: I660742b0cb13297a6489fa340be52e372a91112a
diff --git a/src/com/android/providers/calendar/CalendarProvider2.java b/src/com/android/providers/calendar/CalendarProvider2.java
index 5b78b50..a85c45b 100644
--- a/src/com/android/providers/calendar/CalendarProvider2.java
+++ b/src/com/android/providers/calendar/CalendarProvider2.java
@@ -5057,7 +5057,9 @@
         }
 
         // make sure the widget reflects the account changes
-        sendUpdateNotification(false);
+        if (!accountsToDelete.isEmpty()) {
+            sendUpdateNotification(false);
+        }
     }
 
     /**