Fix matching for cleanup check.

The onlyif check was incorrectly specified in the original implementation in
commit id: 15b83d88 this inverts it so it
is properly detected.

Change-Id: I531e206fff1ca61780adcd195e1f917011e50fb4

puppet/modules/site_postfix/manifests/mx.pp

@@ -96,7 +96,7 @@ class site_postfix::mx {
   # access the opendkim milter socket (#8020)
   exec { 'unset_cleanup_chroot':
     command => '/usr/sbin/postconf -F "cleanup/unix/chroot=n"',
-    onlyif  => '/usr/sbin/postconf -h -F "cleanup/unix/chroot" | egrep -q ^n',
+    onlyif  => '/usr/sbin/postconf -h -F "cleanup/unix/chroot" | egrep -qv ^n',
     notify  => Service['postfix'],
     require => File['/etc/postfix/master.cf']
   }