Include the x509certs class when needed.

The named_vhost.conf.erb template file references variables in the
x509certs class when the 'certname' parameter of apache::named_vhost
is specified.  We need to include the class to make sure the variables
are available.

The variable references happened to work anyway in many practical
cases, where the user used the x509certs module in other ways, but
it isn't right to depend on that.

manifests/named_vhost.pp

@@ -58,6 +58,9 @@ define apache::named_vhost($urls,
     case $ensure
     {
 	'present': {
+	    if $certname {
+		include x509certs
+	    }
 	    apache::include_file {
 		"vhost-${name}":
 		    content => template('apache/named_vhost.conf.erb'),