Do not scan for workspaces on Readdir.

Finding the workspace for a given backing store is a common operation
that requires readdir, and should not be expensive.

unionfs/autounion.go

@@ -332,7 +332,6 @@ func (me *AutoUnionFs) OpenDir(name string) (stream chan fuse.DirEntry, status f
 	case _STATUS:
 		return me.StatusDir()
 	case _CONFIG:
-		me.updateKnownFses()
 	case "/":
 		name = ""
 	case "":

unionfs/autounion_test.go

@@ -90,6 +90,12 @@ func TestAutoFsSymlink(t *testing.T) {
 	log.Println("sleeping...")
 	time.Sleep(2 * entryTtl * 1e9)
 
+	scan := wd + "/mount/config/" + _SCAN_CONFIG
+	err = ioutil.WriteFile(scan, []byte("something"), 0644 )
+	if err != nil {
+		t.Error("error writing:", err)
+	}
+
 	fi, _ = os.Lstat(wd + "/mount/manual1")
 	if fi != nil {
 		t.Error("Should not have file:", fi)