Improve quota logic to dedup code and use waterfall properly

Issue: CLDSRV-669

Author: Seragonia

lib/api/completeMultipartUpload.js

@@ -569,39 +569,28 @@ function completeMultipartUpload(authInfo, request, log, callback) {
                             extraPartLocationsCount: extraPartLocations.length,
                             error: err,
                         });
-
-                        // Continue with quota validation but don't fail if it errors either
-                        return validateQuotas(request, destinationBucket, request.accountQuotas,
-                            ['objectDelete'], 'objectDelete', -droppedMPUSize, false, log, quotaErr => {
-                                if (quotaErr) {
-                                    log.warn('failed to update inflights after extra part deletion failure', {
-                                        method: 'completeMultipartUpload',
-                                        error: quotaErr,
-                                    });
-                                }
-                                // Always succeed - the core operation was successful
-                                return next(null, destinationBucket, aggregateETag, generatedVersionId);
-                            });
                     }
-
-                    return validateQuotas(request, destinationBucket, request.accountQuotas,
-                        ['objectDelete'], 'objectDelete', -droppedMPUSize, false, log, err => {
-                            if (err) {
-                                // Ignore error, as the data has been deleted already: only inflight count
-                                // has not been updated, and will be eventually consistent anyway
-                                log.warn('failed to update inflights', {
-                                    method: 'completeMultipartUpload',
-                                    extraPartLocations,
-                                    error: err,
-                                });
-                            }
-                            return next(null, destinationBucket, aggregateETag,
-                                generatedVersionId);
-                    });
+                    return next(null, destinationBucket, aggregateETag,
+                        generatedVersionId, droppedMPUSize);
                 });
             }
             return next(null, destinationBucket, aggregateETag,
-                generatedVersionId);
+                generatedVersionId, droppedMPUSize);
+        },
+        function updateQuotas(destinationBucket, aggregateETag, generatedVersionId, droppedMPUSize, next) {
+            return validateQuotas(request, destinationBucket, request.accountQuotas,
+                ['objectDelete'], 'objectDelete', -droppedMPUSize, false, log, err => {
+                    if (err) {
+                        // Ignore error, as the data has been deleted already: only inflight count
+                        // has not been updated, and will be eventually consistent anyway
+                        log.warn('failed to update inflights', {
+                            method: 'completeMultipartUpload',
+                            error: err,
+                        });
+                    }
+                    return next(null, destinationBucket, aggregateETag,
+                        generatedVersionId);
+            });
         },
     ], (err, destinationBucket, aggregateETag, generatedVersionId) => {
         const corsHeaders =