Fix bug #5713 by correcting the generated schema.

Fix bug #5713 by correcting the generated schema.

This bug is entitled 'Schema patch breaks interoperability with
Microsoft MMC consoles.', and it does so very spectacularly.

The issue is that we would include an entry:
objectClasses: ( 2.5.6.0 NAME 'top' SUP top ABSTRACT..

The MMC Active Directory Users and Computers snap in presumably
objected to the 'loop' this would present. The fixed entry is:

objectClasses: ( 2.5.6.0 NAME 'top' ABSTRACT

Thanks to Matthias Dieter Wallnöfer <mwallnoefer@yahoo.de> for his
persistance in getting me to look at this.

Andrew Bartlett
(This used to be commit 937b466266256d26d02cf8d48e72a26272fe8627)