s4-dsdb/schema_syntax: Separate validation for numericoid OID values

s4-dsdb/schema_syntax: Separate validation for numericoid OID values

This implementation doesn't use prefixMap/Schema to validate
numericoid OIDs. We may not have this OID yet, so I see no point
checking schema for if we have it.

Side effect of using prefixMap/Schema for validating numericoids
is that we mistakenly add the OID to the prefixMap.
This led to a corrupted prefixMap in LDB.

Autobuild-User: Kamen Mazdrashki <kamenim@samba.org>
Autobuild-Date: Thu Oct 21 23:32:26 UTC 2010 on sn-devel-104