vol-salvage: Only delete bad vnodes during !check

vol-salvage: Only delete bad vnodes during !check

In SalvageIndex, if check is true, we're only supposed to check for
consistency and not actually change anything (this is enforced by an
assert later on). The check for vnode magic consistency breaks this
assumption, and just always fixes the vnode.

Change this so we just error out if check is set, and the vnode magic
is wrong.

Reviewed-on: http://gerrit.openafs.org/3756
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 5817a13b84496c087b350be50c17a8b0f9aac9d5)

Change-Id: I1b12c56d680111ba71b611ab9bbb6159a35dd14e
Reviewed-on: http://gerrit.openafs.org/3866
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>