Updated ObjectProxy.CheckInvariants.
Updated ObjectProxy.CheckInvariants.

kahing/gcsfuse,BanzaiMan/gcsfuse,BanzaiMan/gcsfuse,jacobsa/ratelimit,GoogleCloudPlatform/gcsfuse,jacobsa/timeutil,mbrukman/gcsfuse,GoogleCloudPlatform/gcsfuse,GoogleCloudPlatform/gcsfuse