volser: Preserve needsSalvaged during restore

volser: Preserve needsSalvaged during restore

Some of the routines during a volume restore may set needsSalvaged, if
an inconsistency is detected while writing the given volume data.
However, after the data is read, we set the volume header information
to what was found in the dump stream, ignoring any needsSalvaged that
may have been set.

To ensure that inconsistent volumes in this situation actually get
demand-salvaged (for DAFS) or offlined (non-DAFS), keep the value of
needsSalvaged in the header, if it was set.

Change-Id: I575d14d84120be0fbbeb185ed2726f1285e6f2ce
Reviewed-on: http://gerrit.openafs.org/5822
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>