Publish .log files as text/plain

Default apache mimetypes don't include .log as text/plain; add it.
Log export was added with I67870f6d439af2d2a63a5048ef52cecff3e75275 so
match the .log.1 file that logrotate creates for our rsync mirror logs
too.

Change-Id: Iaf3f19d26f3a6fda7ef3571573af219a31f1dced

playbooks/roles/mirror/templates/mirror.vhost.j2

@@ -112,6 +112,8 @@ ErrorLogFormat "[%{cu}t] [%-m:%l] [pid %P:tid %T] %7F: %E: [client\ %a] %M% , \
     CustomLog /var/log/apache2/mirror_$port_access.log combined-cache
     ServerSignature Off
 
+    AddType text/plain .log .log.1
+
 </Macro>
 
 <VirtualHost *:80>