[Fix confirmCredntials flow]

This CL contains 2 fixes:

1. On a successfult confirm credential, lastAuthenticatedTime was
   not getting updated. This gets fixed.

2. Historically, confirmCredential used to work for accounts NOT on
   the device. Setting lastAuthenticated time only for existing
   accounts and preventing crash if account is not on the device.

Bug: 20141809
Change-Id: I301d49cbc4a594af6110366ef6f55350f74d250d
1 file changed