Fix build due to previous LXC patch

Mark virDomainLxcEnterNamespace as skipped in python binding
and remove reference to lxcDomainOpenNamespace which doesn't
arrive until a later patch

python/generator.py

@@ -530,6 +530,7 @@ skip_function = (
 )
 
 lxc_skip_function = (
+  "virDomainLxcEnterNamespace",
 )
 qemu_skip_function = (
     #"virDomainQemuAttach",