When manpages are displayed on a terminal, <literal>s are indistinguishable
from surrounding text. Add quotes everywhere, remove duplicate quotes,
and tweak a few lists for consistent formatting.
https://bugzilla.redhat.com/show_bug.cgi?id=874631
https://bugs.freedesktop.org/show_bug.cgi?id=55890
Fixed typos, serial comma, and removed "either" as there were more
than two options. Also did an extra rename of "system-shutdown"
to "systemd-shutdown" that was forgotten in commit
8bd3b8620c
