add instructions to remove aliases without reboot

[weideng1]

No description provided.

[joao-r-reis]

@adutra do you want to give this a go on your Mac just as a simple check before we merge this?

[adutra]

I wonder if we shouldn't redesign the example scripts a bit. Opening 255 addresses on 4 subnets is too much and will definitely incur in the mdns responder issue described in the text (it does on my machine).

I'd suggest to change the snippets and:

1. Only open aliases in 2 subnets;
2. Only open 50 aliases in each subnet.

That's more than enough for most usages of Simulacron imo.

[adutra]

Suggested change

	for i in {0..255}; do sudo ifconfig lo0 -alias 127.0.$sub.$i; done
	for i in {0..255}; do sudo ifconfig lo0 -alias 127.0.$sub.$i down; done

[adutra]

Also note: this is bringing 127.0.0.0 and 127.0.0.1 down. I don't know if that's safe, even if 127.0.0.1 is being brought up again later in the same script.

[adutra]

See https://apple.stackexchange.com/questions/386721/how-to-stop-mdnsresponder-from-using-90-100-cpu-continuously-forever-on-catalin for details.