deleting default wallet before syncing

If we are sure a user is in first-run mode, have an empty wallet, and are signing into a synced account, we should delete the default account before syncing. IThis should be the case every time for Android. 

f we don't every time they sign-in on a new device will result in an additional blank account being synced. This means an additional 26 wallet addresses need to be subscribed to. 