Fix another gentoo template typo

I've found one more typo in the gentoo template, configuration in the
generated file /etc/conf.d/hostname was not valid, but it didn't impact
me due to "lxc.utsname" being set in the configuration file of container
and hostname service being not used. Anyway, I've made a patch and
sending it with this mail.

Signed-off-by: Dark Templar <dark_templar@hotbox.ru>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>