Set earlyBootEnded before apex starts

earlyBootEnded signals to keystore2 to read the database for the first
time, and start the MAX_BOOT_LEVEL system. It must therefore run
after /data is mounted and /data/misc/keystore is created, but before
apexd or odsign starts.

Bug: 176450483
Test: cuttlefish: check keystore2 logs to ensure all looks well.
Change-Id: Ia3b968afc38edf95712480e99e545ba88ea309c3