dafs: honor salvageserver -salvagedirs

dafs: honor salvageserver -salvagedirs

Do not ignore the -salvagedirs option when given to the salvageserver.
When the salvageserver is running with this option, all directories will
be rebuilt by salvages spawned by the dafs salvageserver, including all
demand attach salvages and salvages of individual volumes initiated by
bos salvage.

This does not affect the whole partition salvages initiated by bos
salvage -all.

Reviewed-on: https://gerrit.openafs.org/12456
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Tested-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
(cherry picked from commit 9e66234951cca3ca77e94ab431f739e85017a23a)

Change-Id: I121299a5524cb46a519aead7818b0a7bd2fd4f69
Reviewed-on: https://gerrit.openafs.org/12461
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>