dafs: avoid asserting on dafs VSALVAGING error code
DAFS introduced the VSALVAGING error code which is returned when a vnode
cannot be put and a volume has been scheduled to be salvaged.
Update the afsfileprocs to not assert on VSALVAGING, as well as the
VSALVAGE error code.
For example, VPutVnode() and VVnodeWriteToRead() may call
VRequestSalvage_r() which will set the error code to VSALVAGING when a
salvage is requested.
This was noticed during a code inspection.
Change-Id: I6cacfe92347bc5af57defef17b8a2f98c5302f93
Reviewed-on: http://gerrit.openafs.org/10611
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>