Remove rmilter from mailserver configuration

Rmilter [is no longer
needed](https://rspamd.com/doc/quickstart.html#rmilter-setup) as of
Rspamd 1.6.

roles/mailserver/DESIGN.md

+# Design Description for Mailserver Role
+
+## Mail filters
+
+Four mail filters are used:
+
+* [Postgrey](http://postgrey.schweikert.ch/), which runes on port 10023 and is hooked into postfix with the `smtpd_recipient_restrictions` variable;
+* [OpenDKIM](http://www.opendkim.org/), which runs on port 8891;
+* [OpenDMARC](http://www.trusteddomain.org/opendmarc/), which runs on port 54321; and
+* [Rspamd](https://rspamd.com), which runs on port 11332.
+
+OpenDKIM, OpenDMARC, and Rspamd are all hooked into postfix with the `smtpd_milters` variable.  All of this can be found in `etc_postfix_main.cf`.

roles/mailserver/files/etc_rmilter.conf.common

-spamd {
-	servers = r:localhost:11333;
-	whitelist = 127.0.0.1/32, 192.168.0.0/16, [::1]/128;
-};
-
-redis {
-	servers_id = localhost;
-	id_prefix = "message_id.";
-};
-
-tempdir = /tmp;
-max_size = 10M;

roles/mailserver/files/lib_systemd_system_rmilter.socket

-[Unit]
-Description=Another sendmail milter for different mail checks
-
-[Socket]
-ListenStream=9900
-
-[Install]
-WantedBy=sockets.target

roles/mailserver/tasks/rspamd.yml

   tags:
     - dependencies
 
-- name: Install Rspamd, Rmilter, and Redis
+- name: Install Rspamd and Redis
   apt: pkg={{ item }} state=installed update_cache=yes
   with_items:
     - rspamd
-    - rmilter
     - redis-server
   tags:
     - dependencies
 
-- name: Configure rmilter.common
-  copy: src=etc_rmilter.conf.common dest=/etc/rmilter.conf.common
-
-- name: Configure rmilter socket
-  lineinfile: dest=/etc/rmilter.conf regexp=^bind_socket line="bind_socket = inet:9900@localhost;"
-
-- name: Configure rmilter service
-  copy: src=lib_systemd_system_rmilter.socket dest=/lib/systemd/system/rmilter.socket
-
 - name: Start redis
   service: name=redis-server state=started
 
 - name: Start rspamd systemd listener
   service: name=rspamd state=started
-
-- name: Start rmilter systemd listener
-  service: name=rmilter state=started

roles/mailserver/templates/etc_postfix_main.cf.j2

 local_recipient_maps = $virtual_mailbox_maps
 
 # Milters: OpenDKIM, OpenDMARC, Rspamd
-smtpd_milters = inet:127.0.0.1:8891,inet:127.0.0.1:54321,inet:127.0.0.1:9900
+smtpd_milters = inet:127.0.0.1:8891,inet:127.0.0.1:54321,inet:127.0.0.1:11332
 non_smtpd_milters = $smtpd_milters
 milter_protocol = 6
 milter_mail_macros = i {mail_addr} {client_addr} {client_name} {auth_authen} {auth_type}