Deal with mismatch between our accounts and AccountManager accounts

* Addresses #2226426
* Recognize the case in which there is no EmailProvider Account corresponding
  to an AccountManager account (the case being addressed is that of the
  EmailProvider database being deleted due to corruption
* In this case, delete the AccountManager account so that the two are in
  sync
* Refactor and add unit test for account reconciliation

Change-Id: I356b8bfaa0846f85223cc15994b750df207a63ea
2 files changed