Add post-deploy and post-rollback hooks

These replace the custom audit_broadcast_cmd code. An additional env
variable MRSK_RUNTIME is passed to them.

The audit broadcast after booting an accessory has been removed.

test/integration/docker/deployer/app/.mrsk/hooks/post-deploy

@@ -0,0 +1,3 @@
+#!/bin/sh
+echo "Deployed!"
+mkdir -p /tmp/${TEST_ID} && touch /tmp/${TEST_ID}/post-deploy

test/integration/docker/deployer/app/.mrsk/hooks/post-rollback

@@ -0,0 +1,3 @@
+#!/bin/sh
+echo "Rolled back!"
+mkdir -p /tmp/${TEST_ID} && touch /tmp/${TEST_ID}/post-rollback