Move UMS.markEphemeralUsersForRemoval earlier in the boot.

When the device is rebooted with an ephemeral user existing, after the
reboot UserManager.getAliveUsers() was containing that user as well,
which was causing a FATAL exception in BiometricScheduler during boot.

This CL fixes that issue by moving the markEphemeralUsersForRemoval
earlier.

Bug: 327972305
Test: atest CtsMultiUserHostTestCases
Flag: None
Change-Id: I240025cdd27a7b9b3eb89b241e14cbd75aad5d26