Merge heal dry-run fixes (#280)

Takes the dry-run part of PR #280 and credits its author. The parallel deep-verification part stays in #280 for separate review.

cmd/peer-rest-server.go

@@ -1292,8 +1292,10 @@ func (s *peerRESTServer) HealBucketHandler(mss *grid.MSS) (np *grid.JSON[madmin.
 	}
 
 	bucketDeleted := mss.Get(peerS3BucketDeleted) == "true"
+	dryRun := mss.Get(peerS3BucketDryRun) == "true"
 	res, err := healBucketLocal(context.Background(), bucket, madmin.HealOpts{
 		Remove: bucketDeleted,
+		DryRun: dryRun,
 	})
 	if err != nil {
 		return np, grid.NewRemoteErr(err)