[Fix extra data in cache]

It seems that some account authenticators call getData before account
is added, which initializes the cache for that account.
1. We now don't initialize the cache if the account is not on the device.
2. We now use locking.

Bug: 23018710
Bug: 20071745
Change-Id: Ie59ca6b4e575f524a9d3bf286c3bd95abce4a596