Use isCeStorageUnlocked() in AMS.maybeSendBootCompletedLocked()

isUserKeyUnlocked() is being renamed to isCeStorageUnlocked() to make it
clear what it does (considering that there are many types of user keys).
Temporarily, the method exists under both names.  Change
ActivityManagerService#maybeSendBootCompletedLocked() to use the new
name.  No change in behavior.

Bug: 306204742
Flag: exempt, mechanical refactoring
Test: presubmit
Ignore-AOSP-First: code was added by ag/25096398, not in AOSP yet
Change-Id: I977d213854ee0bd047b65cdc96dcab5ce3396701