Restore resetKeyStore() logic of clearing SYSTEM uid

Keystore no longer clears keys critical to device encryption flow
so no need to skip clearing SYSTEM's keystore entries here.

Bug: 34600579
Test: Add device lock under synthtic password, goto Settings/security/encryption,
      tap clear credentials and verify device lock is still intact.
Change-Id: I191a545181771693fd2d75f1c23d14a6b74278af
Merged-In: I191a545181771693fd2d75f1c23d14a6b74278af