mongodb: the server container is mongodb-server, not the predecessor's name

The adopted node still runs the predecessor's mongo container, and it must
keep running: invoicing points at novox.be:27017 and is not migrating in
this window. A module container named 'mongo' would be held at assign and
would replace the predecessor at take, cutting invoicing off its database.
The mesh's server coexists instead — fresh data directory, its own name,
auto-allocated machine port — and the predecessor retires with its last
consumer.

modules/mongodb/module.json

@@ -75,7 +75,7 @@
     {
       "id": "server",
       "type": "container",
-      "name": "mongo",
+      "name": "mongodb-server",
       "image": "mongo@sha256:e3fa459b4f4b72f3257c67a23c145e250b8b5700f033860392c68539b998bbe3",
       "network": "mongodb",
       "env": {
@@ -101,7 +101,7 @@
         "/var/lib/mongodb/root.secret:/run/secrets/root:ro"
       ],
       "env": {
-        "MESH_PROVISION_MONGODB": "mongodb://root@mongo:27017/admin?authSource=admin",
+        "MESH_PROVISION_MONGODB": "mongodb://root@mongodb-server:27017/admin?authSource=admin",
         "MESH_PROVISION_PASSWORD_FILE": "/run/secrets/root",
         "MESH_BROKER_FILE": "/run/secrets/broker",
         "MESH_RECEIVES": "/var/lib/mongodb/grants/mesh.json"