Merge pull request #1547 from giuseppe/make-unsupported-fs-a-debug-msg

overlay: change error to debug log for unsupported fs

drivers/overlay/overlay.go

@@ -314,9 +314,6 @@ func Init(home string, options graphdriver.Options) (graphdriver.Driver, error)
 	}
 	fsName, ok := graphdriver.FsNames[fsMagic]
 	if !ok {
-		if opts.mountProgram == "" {
-			return nil, fmt.Errorf("filesystem type %#x reported for %s is not supported with 'overlay': %w", fsMagic, filepath.Dir(home), graphdriver.ErrIncompatibleFS)
-		}
 		fsName = "<unknown>"
 	}
 	backingFs = fsName