fix(shell): change prefix for health checks

Since Pongo sets the prefix to use to `/kong-plugin/servroot/` the
healthchecks would always fail because they would check in the
default location. This fixes them.

Health is ok, if Kong is running in the container.
So in case of a `pongo shell` it is unhealthy until Kong is started.

assets/docker-compose.yml

@@ -152,6 +152,16 @@ services:
       - PONGO_COMMAND=${ACTION}
       - PONGO_NETWORK=${SERVICE_NETWORK_NAME}
       - PONGO_ID=${PROJECT_ID}
+    healthcheck:
+      interval: 5s
+      retries: 10
+      test:
+      - CMD
+      - kong
+      - health
+      - --prefix=/kong-plugin/servroot/
+      timeout: 10s
+      disable: ${SERVICE_DISABLE_HEALTHCHECK:-false}
     networks:
       pongo-test-network:
         aliases: