util: Move recwatch package to util directory

This makes more sense and this is also a reminded that it needs a bit of
a cleanup.

engine/resources/group.go

@@ -40,8 +40,8 @@ import (
 
 	"github.com/purpleidea/mgmt/engine"
 	"github.com/purpleidea/mgmt/engine/traits"
-	"github.com/purpleidea/mgmt/recwatch"
 	"github.com/purpleidea/mgmt/util/errwrap"
+	"github.com/purpleidea/mgmt/util/recwatch"
 )
 
 func init() {