bos: Remove MR-AFS commands and options

bos: Remove MR-AFS commands and options

The blockscanner and unblockscanner commands, as well as many options
to "bos salvage", were only of use to MR-AFS. MR-AFS is not used
anywhere anymore, and these commands and options were largely
undocumented, so get rid of them. See
<https://lists.openafs.org/pipermail/openafs-info/2013-January/039215.html>.
Thanks to Hartmut Reuter for providing information about this.

Change-Id: I496eb4a23a0310aafd6c224a08c76a8b7464c758
Reviewed-on: http://gerrit.openafs.org/10425
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>