More thorough cleansing of expired users

If any /data/system_[c|d]e folders were not erased
when the user was removed (maybe due to a reboot),
make sure they're cleaned up on restart as well
as when the userId is recycled later.

Mark the users' system folders with the correct
serial number for later verification.

AccountManager shouldn't be querying accounts of
partially created/destroyed users.

Change-Id: I4313756b7464f34cd5ce4fb296d61daa50b41fcb
Fixes: 29285673