make part and mms insertion a single transaction

fixes #3051
closes #3059
// FREEBIE

src/org/thoughtcrime/securesms/database/MmsDatabase.java

@@ -749,6 +749,8 @@ public class MmsDatabase extends MessagingDatabase {
 
     contentValues.put(PART_COUNT, PartParser.getSupportedMediaPartCount(body));
 
+    db.beginTransaction();
+    try {
       long messageId = db.insert(TABLE_NAME, null, contentValues);
 
       addressDatabase.insertAddressesForId(messageId, headers);
@@ -756,8 +758,12 @@ public class MmsDatabase extends MessagingDatabase {
 
       notifyConversationListeners(contentValues.getAsLong(THREAD_ID));
       DatabaseFactory.getThreadDatabase(context).update(contentValues.getAsLong(THREAD_ID));
-
+      db.setTransactionSuccessful();
       return messageId;
+    } finally {
+      db.endTransaction();
+    }
+
   }
 
   public boolean delete(long messageId) {