Clean-ups for EmailProvider

- Don't allow manual modification of unreadCount/messageCount
  (We used to check only unreadCount in update().)
- Do the integrity check at the very first in update().
  I think the old place was really problematic because we opened
  the database in a few lines above and kept it in a local variable.

Change-Id: I2bf5de4e4e45b40c11b951dd2255f8193c26f1aa
1 file changed