Use the correct name for apache

The name of the apache package and service are different on different
operating systems. Fortunately, the apache module populates a variable
with the correct name for us. This is also true of the apache ssl
package.

Change-Id: I7d93e56281f828cba9262c135b0beb43dce9748a

manifests/init.pp

@@ -25,7 +25,7 @@ class mailman($vhost_name=$::fqdn) {
     group   => 'root',
     replace => true,
     mode    => '0444',
-    require => Package['apache2'],
+    require => Package[$::apache::params::apache_name],
   }
 
   file { '/etc/mailman/mm_cfg.py':