b/10211620
The problem here is that on app upgrade, we need to change
the types of all email accounts. To do this, we have to
create new accounts and delete the old ones. This resulted
in calendar and contacts data getting deleted.
But we were copying over the last sync keys from the old
account, so on the next sync, we would only get new data.
This means that all of the data that we had gotten on
a previous sync would never be sent again, so calendar
events and contacts would be missing forever.
Now, we just don't migrate the old sync keys. This means
that on the next sync, we'll get all data, and restore
our original state.
This is still not ideal, because it means that any locally
created data that has not yet been synced will be lost
(b/10805685), but it's much better than it was.
Change-Id: I150c4dbdf490a8f3880261e2469795896ebfeab5
7d6d8c87f8