Wire postgres credentials into SOC module config

- Create vars/postgres.map.jinja for postgres auth globals
- Add POSTGRES_GLOBALS to all manager-type role vars
  (manager, eval, standalone, managersearch, import)
- Add postgres module config to soc/defaults.yaml
- Inject so_postgres credentials from auth pillar into
  soc/defaults.map.jinja (conditional on auth pillar existing)

salt/vars/manager.map.jinja

@@ -1,12 +1,14 @@
 {% from 'vars/elasticsearch.map.jinja' import ELASTICSEARCH_GLOBALS %}
 {% from 'vars/logstash.map.jinja' import LOGSTASH_GLOBALS %}
+{% from 'vars/postgres.map.jinja' import POSTGRES_GLOBALS %}
 
 {% set ROLE_GLOBALS = {} %}
 
 {% set MANAGER_GLOBALS =
    [
      ELASTICSEARCH_GLOBALS,
-     LOGSTASH_GLOBALS
+     LOGSTASH_GLOBALS,
+     POSTGRES_GLOBALS
    ]
 %}