salvager: fix filesystem path truncation

salvager: fix filesystem path truncation

Fix filesystem path truncation for vice partitions beyond /vicepz.

Commit 3d7388b7 moved the filesystem path to a fixed size buffer,
however the path of the filesystem to be salvaged is truncated for
partitions with two character ids (e.g. /vicepaa), in which case
the salvager will salvager the wrong partition, or abort if the
truncated path is not present.

(cherry picked from commit 1e487f6026fb559638fab256362dbda9d4b4a8b1)

Change-Id: I1f69b580e4db59f9e8dc245348ede176fc1d23c1
Reviewed-on: http://gerrit.openafs.org/5474
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>