mosquitto: run mosquitto_ctrl inside the broker's container

The module's code moved out of its container and took mosquitto_ctrl from a host package. A
machine whose package index is stale cannot install it (hq issue 205), so the tools failed. The
broker's own image carries the tool at the broker's version: the tools exec into the running
broker, and the bootstrap seeds from a throwaway container of the same image.

modules/mosquitto/module.json

@@ -92,7 +92,7 @@
       "type": "file",
       "path": "${dir:state}/bootstrap.env",
       "mode": "0600",
-      "content": "MESH_PROVISION_MQTT=127.0.0.1:${port:1883}\nMESH_PROVISION_ADMIN_USER=mesh-admin\nMESH_PROVISION_PASSWORD_FILE=${dir:mesh-state}/admin\nMESH_DYNSEC_FILE=${dir:data}/dynamic-security.json\n"
+      "content": "MESH_PROVISION_MQTT=127.0.0.1:${port:1883}\nMESH_PROVISION_ADMIN_USER=mesh-admin\nMESH_PROVISION_PASSWORD_FILE=${dir:mesh-state}/admin\nMESH_DYNSEC_FILE=${dir:data}/dynamic-security.json\nMESH_MQTT_CTRL_IMAGE=eclipse-mosquitto@sha256:38c0da4f2ef84284d47b3b3eeea1cb3bdeabe81ee10caf0cd5c5ff61ee3ea408\n"
     },
     {
       "id": "bootstrap",
@@ -125,11 +125,6 @@
         "${dir:data}:/mosquitto/data",
         "${dir:state}/mosquitto.conf:/mosquitto/config/mosquitto.conf:ro"
       ]
-    },
-    {
-      "id": "client",
-      "type": "package",
-      "package": "mosquitto"
     }
   ],
   "build": {
@@ -153,7 +148,8 @@
           "MESH_RECEIVES": "${dir:grants}/mesh.json",
           "MESH_PROVISION_MQTT": "127.0.0.1:${port:1883}",
           "MESH_PROVISION_ADMIN_USER": "mesh-admin",
-          "MESH_PROVISION_PASSWORD_FILE": "${dir:mesh-state}/admin"
+          "MESH_PROVISION_PASSWORD_FILE": "${dir:mesh-state}/admin",
+          "MESH_MQTT_CTRL_CONTAINER": "mosquitto"
         }
       }
     ]