[Shtoom] note: unit tests

[Anthony Baxter]

After some hints from warner and radix on #twisted, I've had it
explained to me (using very small words) what I was doing wrong
in the callcontrol tests, and I've fixed the unit tests so that
they're working again.

Adding more sounds like an _excellent_ idea. I _hope_ the current
test_callcontrol.py code is obvious enough...

For those playing along at home, there's now a #shtoom channel on
irc.freenode.net. If I'm on-line, I'll be on that channel.

Anthony