network: Fix rare race condition with sysctl
network: Fix rare race condition with sysctl

On very busy systems (like our Jenkins), a network interface may
disappear between the time we list the interfaces and the time we
attempt to set the sysctl, so just ignore ENOENT.

Signed-off-by: Stéphane Graber <089afc6d81f66f1168a9849e15660feae286e024@ubuntu.com>

chrisglass/lxd,lxc/lxd,jsavikko/lxd,Skarlso/lxd,mjeanson/lxd,stgraber/lxd,georghopp/lxd,akshaykarle/lxd,hallyn/lxd,chrisglass/lxd,erikmack/lxd,hallyn/lxd,stgraber/lxd,chrisglass/lxd,erikmack/lxd,atxwebs/lxd,mjeanson/lxd,techtonik/lxd,hallyn/lxd,lxc/lxd,stgraber/lxd,hallyn/lxd,hallyn/lxd,lxc/lxd,erikmack/lxd,pcdummy/lxd,stgraber/lxd,lxc/lxd,georghopp/lxd,jsavikko/lxd,hallyn/lxd,ollie314/lxd,pcdummy/lxd,stgraber/lxd,lxc/lxd,atxwebs/lxd,pcdummy/lxd,mjeanson/lxd,stgraber/lxd,georghopp/lxd,jsavikko/lxd,stgraber/lxd,techtonik/lxd,atxwebs/lxd,lxc/lxd,Skarlso/lxd,ollie314/lxd,techtonik/lxd,Skarlso/lxd,lxc/lxd,ollie314/lxd,atxwebs/lxd,akshaykarle/lxd,Skarlso/lxd,akshaykarle/lxd