Bug 706179 - DS can not restart after create a new objectClass has
entryusn attribute
https://bugzilla.redhat.com/show_bug.cgi?id=706179
Description: entryusn used to be dynamically added in the backend
init, which occurred after the schema initialization. And it made
the server's start-up fail when an objectclass contains entryusn
as its attribute type. This patch adds entryusn to the schema
file.
(cherry picked from commit 9cd075204d7d81a85835b5a42452c8467b0f3594)