added flag to block concurrent mpu completion

Issue : CLDSRV-687

Author: SylvainSenechal

lib/services.js

@@ -579,7 +579,7 @@ const services = {
         const multipartObjectMD = Object.assign({}, params.storedMetadata);
         multipartObjectMD.completeInProgress = true;
         metadata.putObjectMD(params.bucketName, longMPUIdentifier, multipartObjectMD,
-        {}, log, err => {
+        {preventConcurrentComplete: true}, log, err => {
             if (err) {
                 log.error('error from metadata', { error: err });
                 return cb(err);