LockSettingsService: Support for separate clear key api

With the new key management changes for FBE, the keys
are not present in the clear in vold. So, while clearing a pin,
we cannot use the present method to rebound the key to keymaster.

We need to provide the old secret so as to retrieve the key
and then bind it with keymaster.

CRs-Fixed: 2288316

Change-Id: I1dd707513a3d45b62b925fa7bba15babdba9bd1c