Correct hostname and 'root' user in PostgreSQL deployment example (#3682

)

* Correct hostname and 'root' user in PostgreSQL deployment example

* Can't connect to 'defaultdb' because it doesn't exist yet

* Remove unneeded environment variables

examples/deployment/postgresql/docker-compose.yml

@@ -6,9 +6,6 @@ services:
       dockerfile: examples/deployment/docker/db_server/postgresql/Dockerfile
     environment:
       - POSTGRES_HOST_AUTH_METHOD=trust
-      - POSTGRESQL_DATABASE=defaultdb
-      - POSTGRESQL_USER=test
-      - POSTGRESQL_PASSWORD=zaphod
     restart: always # keep the PostgreSQL server running
   trillian-log-server:
     build:
@@ -19,7 +16,7 @@ services:
     command: [
       "--quota_system=postgresql",
       "--storage_system=postgresql",
-      "--postgresql_uri=postgresql:///defaultdb?host=localhost&user=test&password=zaphod",
+      "--postgresql_uri=postgresql:///?host=postgresql&user=postgres",
       "--rpc_endpoint=0.0.0.0:8090",
       "--http_endpoint=0.0.0.0:8091",
       "--alsologtostderr",
@@ -39,7 +36,7 @@ services:
     command: [
       "--quota_system=postgresql",
       "--storage_system=postgresql",
-      "--postgresql_uri=postgresql:///defaultdb?host=localhost&user=test&password=zaphod",
+      "--postgresql_uri=postgresql:///?host=postgresql&user=postgres",
       "--rpc_endpoint=0.0.0.0:8090",
       "--http_endpoint=0.0.0.0:8091",
       "--force_master",