don't change startup mode when using 'Add' button for discovery (bnc #886796)

because it is not common option. You cannot call `GetDiscoveryCmd("a", "b", true, false)`, but can call `GetDiscoveryCmd("a", "b", { only_new: true})`. In fact named parameters is just hash with symbols as keys with predefined values. If you try it from perl, I think it will proof it.