Please review: [389 Project] #579: Error messages encountered when using POSIX winsync

[Noriko Hosoi]

https://fedorahosted.org/389/ticket/579

https://fedorahosted.org/389/attachment/ticket/579/0001-Ticket-579-Error-...

  Bug description: posix_group_fix_memberuid_callback registered by
  posixWinsyncCreateMemberOfTask calls an internal modify function
  even if there are no attributes to fix up.  The attempt fails as
  expected, but it logs cryptic errors in the error log:
    - slapi_modify_internal_set_pb: NULL parameter
    - allow_operation: component identity is NULL

  Fix description: This patch skips calling the fix up internal
  modify if there is no attributes to fix up.