add AFS_DEMAND_ATTACH_UTIL

add AFS_DEMAND_ATTACH_UTIL

use this for non-pthreads "support code" e.g. salvager.

Reviewed-on: http://gerrit.openafs.org/4312
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 04bcfa2821c9deba151f562bb78452276d8d7443)

Change-Id: If956be50059ac128b5880131f961342c2661e5b7
Reviewed-on: http://gerrit.openafs.org/4335
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>