Print where test output is redirected

Also, provide an alternative task that runs tests in foreground,
useful when debugging a test.
Correct connection.blocked test to use set/clear alarm

It was originally based on an old channel.flow test that
did not run and wouldn't work on RabbitMQ versions after 2.0.

This implementation sets and clears alarms the same way
server tests in the Java client do.

Makes make test_network pass.