doc: Symlink all dafssync-debug pages

For every fssync-debug subcommand, provide a symlink for the
associated dafssync-debug subcommand. This way, running e.g.
"man dafssync-debug_attach" will actually give you a manpage, instead
of needing to specifically run "man fssync-debug_attach".

Change-Id: I83d71dc14f9f838d9a9900fcc62817677898dd27
Reviewed-on: http://gerrit.openafs.org/10412
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: Derrick Brashear <shadow@your-file-system.com>