doc: bos setrestricted -mode 0 does make sense

doc: bos setrestricted -mode 0 does make sense

Commit 070230ab76e1df338db3f2a7971111ca976a0c1a added documentation of
the mode parameter to bos setrestricted, claiming that the value 0 is
useless, and commit eee0bf5871944d919951cc8b7b4908ee909c3b62 added
documentation of the restrictmode entry in BosConfig, claiming that it
can only be set back to 0 with an editor. Both claims are wrong, since
bos setrestricted -mode 0 will do exactly that (if it succeeds, which
it only can if the server is running in unrestricted mode, which can
be achieved by sending it the FPE signal). Fix the man pages
accordingly.

Change-Id: I07b75f7d0cea2e247fa4f346121de258e35119f5
Reviewed-on: http://gerrit.openafs.org/10885
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Marc Dionne <marc.c.dionne@gmail.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: D Brashear <shadow@your-file-system.com>