Fix fetchmail syntax errors for fetchmail 6.6.x on Alpine

fetchmailrc.j2:
- Move `ssl` to user section (inline after password); in 6.6.x it is a
  user-level keyword, not a server-level one — placing it after `proto pop3`
  caused 'unexpected USERNAME at user' syntax error
- Move `interval` before user section (it is server-level)
- Replace `smtphost dovecot` + `smtpport 24` with `smtphost dovecot/24`;
  `smtpport` is not a valid rcfile keyword in 6.6.x — port must be given
  as host/port in the smtphost value

dovecot.conf.j2:
- Add `auth_username_format = %Ln` to protocol lmtp block so that the
  LMTP recipient address `ml@dovecot` (appended by fetchmail) is stripped
  to just `ml` for userdb lookup

ansible/roles/mail/templates/fetchmailrc.j2

@@ -6,15 +6,14 @@ set logfile /dev/stdout
 set daemon 60
 
 {% for account in fetchmail_accounts | default([]) %}
-poll {{ account.server }} proto {{ account.protocol | default('pop3') }}{% if account.ssl | default(true) %} ssl{% endif %}
+poll {{ account.server }} proto {{ account.protocol | default('pop3') }}
+  interval {{ account.poll_minutes | default(10) }}
+  user "{{ account.username }}" password "{{ account.password }}"{% if account.ssl | default(true) %} ssl{% endif %}
 
-  user "{{ account.username }}" password "{{ account.password }}"
   is {{ account.local_user }} here
-  smtphost dovecot
-  smtpport 24
+  smtphost dovecot/24
   lmtp
   fetchall
   {{ 'keep' if account.keep | default(true) else 'no keep' }}
-  interval {{ account.poll_minutes | default(10) }}
 
 {% endfor %}