Fix bug that caused task to show behind keyguard

Move guest recreation into the user switch BroadcastReceiver to avoid
lock contention that caused UI bugs in keyguard.

Test: With config_guestUserAutoCreated=true, switch to guest, then
      select reset guest. Ensure that keyguard renders correctly for the
      owner.
Fixes: 193933686
Change-Id: I95ed36dbd2c361312c044dec63a06f1711419131