Prevent Sidekiq from running

Usually we don't want Sidekiq to run during an import because it might mess things up while there's incomplete or inconsistent data.

templates/import/phpbb3.template.yml

@@ -1,5 +1,8 @@
 # This template installs MariaDB and all dependencies needed for importing from phpBB3.
 
+env:
+  UNICORN_SIDEKIQS: 0
+
 params:
   home: /var/www/discourse
 
@@ -15,7 +18,6 @@ hooks:
         cd: /etc/runit/3.d
         cmd:
           - rm 01-nginx
-          - rm 02-unicorn
 
     - file:
         path: /etc/mysql/conf.d/import.cnf