Use a real clock in integration_test.go.
Use a real clock in integration_test.go.

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