Ticket #608 - Posix Winsync plugin throws "posix_winsync_end_update_cb: failed to add task entry" error message
    
    Bug description: When a task posixWinsyncCreateMemberOfTask is
    already running, another same task request is received, the
    Posix Winsync Plug-in issues an error "posix-winsync - posix_
    winsync_end_update_cb: failed to add task entry".  This is not
    an "error" but an expected behaviour.
    
    Fix description: Instead of filing the message as SLAPI_LOG_
    FATAL, this patch logs clearer message "task entry <taskname>
    already exists" if the log level is SLAPI_LOG_PLUGIN.
    posix_winsync_end_update_cb
    
    https://fedorahosted.org/389/ticket/608
    
    Reviewed by Mark (Thank you!!)
    (cherry picked from commit 05803a42892eaf472e863c527545968661b79802)