Tells the proxy not to do anything with this container. We set it when
running weaveexec/weave/etc containers, so that the weave script works
through the proxy.
Pass `-e WEAVE_CIDR=` to your container to use IPAM. If IPAM is not
enabled on the weave router, the container will be booted without weave
networking.
I'm not crazy about adding *another* undocumented weave cli command
(ipam-cidr), but it saves the proxy messing around finding container
IPs.
Bug came up in a test where we are restarting and doing an exec checking
a network interface right away. weavewait is only added if the container
has a WEAVE_CIDR var set, the same as at container creation.
In the proxy, I swapped the 'flag' library for
'code.google.com/p/getopt', which uses double-dash flags.
proxy lets 'weave attach' do dns registration on container start
proxy needs to set DNSSearch if not specified
Bryan Boreham