Code review comment for lp:~vila/bzr/move-test-servers

I forgot to mention that I've put all test servers into
bzrlib.test.test_server because they looked trivial enough
to not need their own dedicated server.

Semy-arbitrarily I left the ftp and http servers out of that
because they needed a bit more code.

The smart servers for testing for a bit between the two but
they needed to leave the bzrlib.transport hierarchy because
they were intended for *test*.