test_logqueue: after changing the refcounter's size of logmsg the MESSAGES_PER_FEEDER is too high

Signed-off-by: Daniel Gados <gdani@balabit.hu>
test: fixed: use backlog queue in threaded testcase, too

Signed-off-by: Budai Laszlo <lbudai@balabit.hu>
logwriter: Fix: NULL ptr can be set as logqueue

Signed-off-by: Budai Laszlo <lbudai@balabit.hu>