Add more integration tests

Add tests for main, app, accessory, traefik and lock commands.
Other commands are generally covered by the main tests.

Also adds some changes to speed up the integration specs:
- Use a persistent volume for the registry so we can push images to to
reuse between runs (also gets around docker hub rate limits)
- Use persistent volume for mrsk gem install, to avoid re-installing
between tests
- Shorter stop wait time
- Shorter connection timeouts on the load balancer

Takes just over 2 minutes to run all tests locally on an M1 Mac
after docker caches are primed.

test/integration/docker/shared/boot.sh

@@ -2,6 +2,4 @@
 
 cp -r * /shared
 
-trap "pkill -f sleep" term
-
-sleep infinity & wait
+exec sleep infinity