Initialize machine_id_checksum. Make unlocking unlocked machine a warning.

Fix issues causing errors in nightly tester:  Attempting to use
machine_id_checksum when it hasn't been initialized; and attempting to
unlock an already unlocked machine causes a fatal error.

Change-Id: Ia149953d4e25c7abf97a189bb5fdd129de865c34
Reviewed-on: https://gerrit-int.chromium.org/42489
Reviewed-by: Yunlian Jiang <yunlian@google.com>
Commit-Queue: Caroline  Tice <cmtice@google.com>
Tested-by: Caroline  Tice <cmtice@google.com>
2 files changed