Revert "[1/2] Separation of lock and encription password."

This reverts commit 80a9599d2ea524303f1bbde095dfcf1738a0b426.
Separate Android Encryption Password from Lockscreen Password

This permits the use of a different (hopefully longer and more complex!) encryption
password, while using a simpler (and easier to type) lockscreen password.

Change-Id: Ia35fdcc769eee8fd7891678a532dafa0f4b3ba04