Add diskpacked-reindex subcommand to camtool

For checking and/or rebuilding index.kv of diskpacked packs.

Change-Id: I1ad87974b2daf58b1e767bb1df6f7b64e8b6359a
Merge "Add diskpacked-reindex subcommand to camtool"
gofmt

Change-Id: I900a49b3f76aec7ef65419f2a5ecaf3eae95defb