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.