Enable Work Profile passphrase verify/write with FBE

When File Based Encryption is present, allow the verify/write of
passphrases to be per-user (it used to always bubble up to the parent
user assuming it is a per-device passphrase).

This is part of the work for the Separate Work Challenge.

Change-Id: I5ae6b7b6ed1dd25aed0843d495b6f5f36e01c4eb