LU-9558 libcfs: handle hotplug state machine

LU-9558 libcfs: handle hotplug state machine

Install the callbacks via the state machine. No functional change.
Lustre was ported to this in linux kernel 4.10

Linux-commit: 7b737965b33188bd3dbb44e938535c4006d97fbb

Lustre was ported to this API in linux kernel 4.10

Change-Id: I4d8dfdf97051f406b2ac5b1cf6015742996fc216
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/27282
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Olaf Weber <olaf.weber@hpe.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>