Open postgres port for import role in DOCKER-USER firewall

When so-postgres was wired in (868cd1187), the import role's firewall
defaults were missed while every other manager-class role (manager,
managerhype, managersearch, standalone, eval) had postgres added to
their DOCKER-USER manager-hostgroup portgroups. As a result, on a
fresh import install the so-postgres container starts but tcp/5432 is
dropped at DOCKER-USER, so soc/kratos/telegraf can't reach it.

Add postgres alongside the existing influxdb entry so import nodes
match the other roles.

salt/firewall/defaults.yaml

@@ -1482,6 +1482,7 @@ firewall:
                 - kibana
                 - redis
                 - influxdb
+                - postgres
                 - elasticsearch_rest
                 - elasticsearch_node
                 - elastic_agent_control