Don't try to lock/unlock already locked/unlocked users

Now that isUserKeyUnlocked() works correctly (even after a userspace
reboot), we can make unlockUserKey() and lockUserKey() be no-ops if the
user is already unlocked/locked.  This avoids misleading log messages.

Bug: 146206679
Test: see I482ed8017f7bbc8f7d4fd5a2c0f58629317ce4ed
Change-Id: I125770c3fa238cb15de9dafb5163e874b4f79cf2