please review ticket 504: allow turning off name2asi and oid2asi table locks

[Ludwig Krispenz]

Please review the following fix for ticket #504

If schema modification is disabled, the access to the attribute syntax 
table can be done without locking.
In that state a client attempt to modify the scema needs to be rejected.

https://fedorahosted.org/389/ticket/504
https://fedorahosted.org/389/attachment/ticket/504/0001-Fix-for-ticket-50...

Regards,
Ludwig