api: Response timeFormat do not need to have nano-second precision.

Fixes an error reported by s3verify.

cmd/api-response.go

@@ -24,10 +24,10 @@ import (
 )
 
 const (
-	timeFormatAMZ  = "2006-01-02T15:04:05.000Z" // Reply date format
-	maxObjectList  = 1000                       // Limit number of objects in a listObjectsResponse.
-	maxUploadsList = 1000                       // Limit number of uploads in a listUploadsResponse.
-	maxPartsList   = 1000                       // Limit number of parts in a listPartsResponse.
+	timeFormatAMZ  = "2006-01-02T15:04:05Z" // Reply date format
+	maxObjectList  = 1000                   // Limit number of objects in a listObjectsResponse.
+	maxUploadsList = 1000                   // Limit number of uploads in a listUploadsResponse.
+	maxPartsList   = 1000                   // Limit number of parts in a listPartsResponse.
 )
 
 // LocationResponse - format for location response.