probe, app: reliable shutdown

- Restructure main funcs for clean defer-stack-unwinds
- Fix Docker container to handle signals properly
- Introduce runsvinit for container init process
- Integration test

scope

@@ -164,6 +164,8 @@ case "$COMMAND" in
             WEAVESCOPE_DNS_ARGS="$WEAVESCOPE_DNS_ARGS --dns $DOCKER_BRIDGE_IP --searchpath $DOMAINNAME"
         fi
 
+        docker rm -f $SCOPE_CONTAINER_NAME >/dev/null 2>&1 || true
+
         CONTAINER=$(docker run --privileged -d --name=$SCOPE_CONTAINER_NAME --net=host --pid=host \
             -v /var/run/docker.sock:/var/run/docker.sock \
             $WEAVESCOPE_DOCKER_ARGS $SCOPE_IMAGE $WEAVESCOPE_DNS_ARGS $SCOPE_ARGS --probe.docker true "$@")
@@ -192,7 +194,6 @@ case "$COMMAND" in
         if ! docker stop $SCOPE_CONTAINER_NAME >/dev/null 2>&1 ; then
             echo "Weave Scope is not running." >&2
         fi
-        docker rm -f $SCOPE_CONTAINER_NAME >/dev/null 2>&1 || true
         ;;
 
     *)