Fix ConcurrentModificationExceptoin in SyncManager

ConcurrentModificationException would be thrown because
we didn't break from the for loop after removing an
entry from the collection we were looping over.

Change-Id: I30435670f76f60b238e29658611b06ec789219aa
Bug: 27136502

services/core/java/com/android/server/content/SyncManager.java

@@ -2546,6 +2546,7 @@ public class SyncManager {
                             Slog.v(TAG, "Pushing back running sync due to a higher priority sync");
                         }
                         deferActiveSyncH(asc);
+                        break;
                     }
                 }
             }