man: Fix documentation errors about the paths of the config files

man: Fix documentation errors about the paths of the config files

The default conf files, for example libvirtd.conf, virtlockd.conf, and
virtlogd.conf, should be located under the directory "/etc/libvirt" when
root as root, rather than "/etc". When run as non-root, the configuration
files should be located under "$XDG_CONFIG_HOME/libvirt/", rather than
"XDG_CONFIG_HOME".

Signed-off-by: Lily Zhu <lizhu@redhat.com>
Signed-off-by: Erik Skultety <eskultet@redhat.com>