Add unit tests for irccd/irccdctl executables
Add tests for the input, output of all executables.
Tests: rework cli_test to spawn irccd daemon in a thread, continue #785
Instead of spawning irccd executable, use the irccd class for better
flexibility in test code.
For example, for server tests we will need to use journal_server to see if
commands have been called instead of checking a real IRC server.
While here, add rule-cli-remove test that was forgotten.