helper: eliminate commandContext replacement

This is done more cleanly by modifying Args in cmdF.

Signed-off-by: Ophestra <cat@gensokyo.uk>

dbus/stub_test.go

@@ -6,6 +6,4 @@ import (
 	"git.gensokyo.uk/security/fortify/helper"
 )
 
-func TestHelperChildStub(t *testing.T) {
-	helper.InternalChildStub()
-}
+func TestHelperStub(t *testing.T) { helper.InternalHelperStub() }