conf: refactor network deletion
conf: refactor network deletion

I'm ashamed at how aweful my previous code was.

Signed-off-by: Christian Brauner <48455ab3070520a2d174545c7239d6d0fabd9a83@ubuntu.com>

thmo/lxc,ss1h2a3tw/lxc,thmo/lxc,ss1h2a3tw/lxc,caglar10ur/lxc,terceiro/lxc,hallyn/lxc,thmo/lxc,terceiro/lxc,caglar10ur/lxc,hallyn/lxc,federicobriata/lxc,terceiro/lxc,caglar10ur/lxc,federicobriata/lxc,federicobriata/lxc,hallyn/lxc,ss1h2a3tw/lxc