Synapse: Change PostgreSQL datadir chmod from 770 to 700.

PostgreSQL datadir permissions are changed to 700 by the container.
Set to 700 from the start to stop the task displaying "changed"
everytime the synaspe role is run.

roles/synapse/tasks/update.yml

@@ -42,7 +42,7 @@
     state: directory
     owner: "{{ users['synapse_postgres'] + uid_shift }}"
     group: "{{ users['synapse_postgres'] + uid_shift }}"
-    mode: '770'
+    mode: '700'
   become: true
 
 - name: Pull project services