lxc: remove unnecessary call to virNetDevReserveName()

lxc: remove unnecessary call to virNetDevReserveName()

In all cases *except* when parsing status XML as libvirt is being
restarted, the XML parser will delete any manually specified interface
name (aka "<target dev='blah'/>" aka net->ifname) that could have been
generated by virNetDevGenerateName(). This means that during the setup
when a domain is being started (e.g. during
virLXCProcessSetupInterfaceTap()) it is pointless to call
virNetDevReserveName() with any setting of net->ifname that has come
from the XML parser - it is guaranteed to not fit the pattern of any
auto-generated name, and so the call is just a NOP anyway.

Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>