roles/postgres: give superuser permission for all DBs

postgres must be able to connect to all databases,
else the postgres_db ansible module is broken.

roles/postgres/templates/pg_hba.conf.j2

@@ -81,7 +81,7 @@
 # TYPE  DATABASE        USER            ADDRESS                 METHOD
 
 # "local" is for Unix domain socket connections only
-local   sameuser        postgres                                peer
+local   all             postgres                                peer
 local   sameuser        all                                     md5
 # IPv4 local connections:
 host    all             postgres        127.0.0.1/32            md5