libafs: stop bkg first

libafs: stop bkg first

because background daemons can have dependence on other subsystems, but
are not needed for other operations, stop them first.

Reviewed-on: http://gerrit.openafs.org/7246
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit e3c93b87b7fa751e9cf4c1356d606b7bb399b06c)

Change-Id: I258519a2ad85af53784cf4db381a7f4a8b429dc8
Reviewed-on: http://gerrit.openafs.org/7485
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>