[Modify LastAuthenticatedTimestamp behaviour]:

We should not modify lastAuthenticated timestamp in authenticator
specific api's, as some of the calls maybe used by authenticators
for internal maintainance/upgrade. Only modify the timestamp when
calls effecting accounts is made to non-authenticator developer api's.

Bug: 21959561

Change-Id: I7b2d0c875957b263c4d9b203fe1f33042a65a58f