libc/cgroups: empty map in RemovePaths

RemovePaths() deletes elements from the paths map for paths that has
been successfully removed.

Although, it does not empty the map itself (which is needed that AFAIK
Go garbage collector does not shrink the map), but all its callers do.

Move this operation from callers to RemovePaths.

No functional change, except the old map should be garbage collected now.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/cgroups/systemd/v1.go

@@ -223,17 +223,14 @@ func (m *legacyManager) Destroy() error {
 	}
 	unitName := getUnitName(m.cgroups)
 
-	err = stopUnit(dbusConnection, unitName)
+	stopErr := stopUnit(dbusConnection, unitName)
 	// Both on success and on error, cleanup all the cgroups we are aware of.
 	// Some of them were created directly by Apply() and are not managed by systemd.
 	if err := cgroups.RemovePaths(m.paths); err != nil {
 		return err
 	}
-	if err != nil {
-		return err
-	}
-	m.paths = make(map[string]string)
-	return nil
+
+	return stopErr
 }
 
 func (m *legacyManager) Path(subsys string) string {