This test ensures that named will correctly shutdown
when receiving multiple control connections after processing
of either "rncd stop" or "kill -SIGTERM" commands.
Before the fix, named was crashing due to a race condition happening
between two threads, one running shutdown logic in named/server.c
and other handling control logic in controlconf.c.
This test tries to reproduce the above scenario by issuing multiple
queries to a target named instance, issuing either rndc stop or kill
-SIGTERM command to the same named instance, then starting multiple rndc
status connections to ensure it is not crashing anymore.
(cherry picked from commit 042e509753)
004849fd36