Fix IPC and TCP test cases.

 - Actually run the tests in IPCSendRecvTest, and fix a few typos.
 - In TCPTest3, close the client in on_client_connection() instead of
   on_connection(), as doing the latter results in calling
   on_client_connection() with error=ECANCELED.

Note that there's a more fundamental issue with many of the unit tests,
more specifically those that use test assertions within callbacks.
Assertions raise an exception, but exceptions aren't propagated out of
callbacks. This results in passing tests, with a stack trace printed to
stdout.