Use SIGHUP instead of SIGTERM to shut down the proxy. The difference

is that SIGTERM tries to tear down everything from the signal handler,
while SIGHUP actually makes main() to exit gracefully so that there
is no racing condition between main() posting event into the rtpp_proc
queue and the rtpp_proc actually exiting.

tests/basic_versions

@@ -18,8 +18,8 @@ do
     ${TOP_BUILDDIR}/python/rtpp_query.py -b -s "${socket}" \
       -S "${TOP_BUILDDIR}/python/sippy_lite" -i $BASEDIR/basic_versions.input -o basic_versions.qout
     report "rtpp_query on ${socket}"
-    rtpproxy_stop TERM
-    report "rtpproxy stop (SIGTERM) on ${socket}"
+    rtpproxy_stop HUP
+    report "rtpproxy stop (SIGHUP) on ${socket}"
     cat basic_versions.qout basic_versions.rout | ${DIFF} ${BASEDIR}/basic_versions.output -
     report "basic_versions on ${socket}"
   fi