currently if more than 500 results on openldap are returned, they will be ignored...
it should rely on its parent class that do handle pagination correctly

fixing this will have a side effect, the search of the 100 first users ask all user to directories... this mean that after the fix, the LDAP impl will return the whole ldap instead of the 500 first... so we should fix first the search of the 100 that should limit to 100