Make the bytecode tests a bit more robust.

They used to require that there were no TCP sockets on the system
at all. Now they only require that there be no established
sockets. Not a huge improvement, but it does make it possible to
write tests that leave-non established sockets around after they
terminate.

(cherry picked from commit 502ceb5ec1e40e65aee8d6acdabd6ae6ec660aef)

Change-Id: Ied6f5aae3b6cf4a5bd25aa4fbeac637010e1f0e8