nodemgr.c::fw_set_rescan() is used to re-run the driver core over
nodemgr's representation of unit directories in order to initiate
protocol driver probes.  It is initiated via write access to one of
nodemgr's sysfs attributes.  The purpose is to attach drivers to
units after switching a unit's ignore_driver attribute from 1 to 0.

It is not really necessary to fork a kernel_thread for this job.  The
call to kernel_thread() can be eliminated to avoid the deprecated API
and to simplify the code a bit.
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Ben Collins <bcollins@ubuntu.com>