Require strong auth after user is stopped

Stopping and restarting a user is equivalent to power cycling
the device, we should require strong auth in this case. This
is particularly important for FBE devices since the user's CE
storage can only be decrypted with strong auth after user restart.

Bug: 69724715
Test: Add guest user with fingerprint, switch to owner and back to
      guest. Verify keyguard requires strong auth.

Change-Id: I9b6b339187cbb82bc9036f0b391babc3c5226378