test: replication/misc cleanup box.cfg.replication

In patch c6bea65f I
added a bug - replication/misc leaves a bad value in
box.cfg.replication. Before that patch the test was
resetting this to empty replication. In my patch I
forgot about that, and left there the value

    {box.cfg.listen, "12345"}

This patch cleans it up.

Follow up #3760

(cherry picked from commit 399899a1)