HealObject should succeed when only N/2 disks have data (#3952)

cmd/xl-v1-utils.go

@@ -41,11 +41,18 @@ func reduceErrs(errs []error, ignoredErrs []error) (maxCount int, maxErr error)
 		}
 		errorCounts[err]++
 	}
+
 	max := 0
 	for err, count := range errorCounts {
-		if max < count {
+		switch {
+		case max < count:
 			max = count
 			maxErr = err
+
+		// Prefer `nil` over other error values with the same
+		// number of occurrences.
+		case max == count && err == nil:
+			maxErr = err
 		}
 	}
 	return max, maxErr