Various ATF manpage fixes

[ngie-eign]

igor/manlint noted various issues with the atf manpages. A full list of commits is here:

• https://svnweb.freebsd.org/changeset/base/314804
• https://svnweb.freebsd.org/changeset/base/314801
• https://svnweb.freebsd.org/changeset/base/314799
• https://svnweb.freebsd.org/changeset/base/314798
• https://svnweb.freebsd.org/changeset/base/314797
• https://svnweb.freebsd.org/changeset/base/314796