Catch FolderSync sync key errors in account validation

* I have no idea how this can happen, but our misconfigured Ex2010
  server is generating a "bad sync key" error in this circumstance,
  and it's causing a crash.

Bug: 5103532
Change-Id: Ib7ff37cdd29087af4de4c0353e9b1b1980ebf648
1 file changed