Fix race condition in Exchange account creation

* Now that observer code has been moved to worker threads, the order
  in which various pieces of account creation are executed has become
  indeterminate
* Because of this, our EasAccountsUpdatedListener could use a stale
  list of EmailProvider accounts when performing reconciliation with
  the AccountManager's list of accounts
* The fix is to ensure that EasAccountsUpdatedListener's worker thread
  causes the cached EmailProvider account list to be updated before
  calling the reconciliation method

Bug: 2558317
Change-Id: Ia94a8301845cf6c06f8efecd408eb237474f781a
1 file changed