Port password retention feature

Password retention feature for HW FDE is needed. Porting from L
release.
This patch also include these changes:
   - Fix clearing of retained password
   - keyguard: Fix password doesnot sanitize after verification
   - LockSettings: fix the get password issue during boot up

Change-Id: I2def56b14c10229b72feccd1c97b281cad65f282