fix storage info output with unordered endpoints arguments (#9610)

Shuffling arguments that we pass to MinIO server are supported. However,
when that happens, Prometheus returns wrong information about disks usage
and online/offline status.

The commit fixes the issue by avoiding relying on xl.endpoints since
it is not ordered.

cmd/posix_windows_test.go

@@ -48,7 +48,7 @@ func TestUNCPaths(t *testing.T) {
 
 	// Instantiate posix object to manage a disk
 	var fs StorageAPI
-	fs, err = newPosix(dir)
+	fs, err = newPosix(dir, "")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -83,7 +83,7 @@ func TestUNCPathENOTDIR(t *testing.T) {
 	defer os.RemoveAll(dir)
 
 	var fs StorageAPI
-	fs, err = newPosix(dir)
+	fs, err = newPosix(dir, "")
 	if err != nil {
 		t.Fatal(err)
 	}