Unlink correct files in salvager

Unlink correct files in salvager

Fallout from 0ac956b3384842b3c60e72bde78a4baf58a5877f; a couple of
unlink() calls were not updated to use the absolute path. Update them,
and log errors from unlink(), since otherwise it is difficult to tell
that anything is going wrong.

Reviewed-on: http://gerrit.openafs.org/479
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>