Keyguard: Don't show when booting to cryptkeeper

Fixes an issue where the keyguard would show if we booted to
cryptkeeper and a SIM PIN is set.

Note that this only happens when the telephony stack gets enabled,
which in cryptkeeper mode is usually only after an emergency call.

Change-Id: I5e5f104189a9d33c356edc181e92409bb63b59d7
Fixes: 64197124
Test: Enter cryptkeeper, make emergency call, verify SIM lock screen does not show.