vol-salvage: Move global vars into SalvInfo struct

vol-salvage: Move global vars into SalvInfo struct

Reduce the number of globals used in the salvager code, by making
functions pass around a 'salvinfo' structure that contains the
information regarding a particular salvage.

Reviewed-on: http://gerrit.openafs.org/2250
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 3d7388b790ef21de552ec60d379764df067ae421)

Change-Id: I15137994806f0c753a42347c28cadcf48002b800
Reviewed-on: http://gerrit.openafs.org/4163
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>