local provider missing network resources under /proc

This is LXC issue and nothing to do with juju-core/local. I can re-produce it in LXC only environment. This ticket can be closed. We will address the issue with LXC.

Well, it might just be part of the required isolation by namespaces.
In fact there is way more missing in /proc/sys comparing a Host to a Container.

sudo sysctl -a | wc -l gives me:
a) # 669 in a wily Container
b) # 1335 in Trusty Host

Since a) and b) essentially share the kernel it should be the same (without isolation).
In fact we can create a List what is missing.
=> missing-in-container.txt

When you first look at it you might think it is a lot, but the major contributor are virtual devices like bridges existing in the Host, but not in the guest.
After cleaning those out of the files the missing lines like this:
=> cleaned-missing-in-container.txt

This was done on an LXD container, I also tried a privileged LXC container but that made no difference.

Still everything that is missing are just network tunables, so it might just be "intended" for network isolation due to network namespaces.
I'm not yet deep into that, but I hope the identified lists help to shorten the bug handling.

Nothing LXC can do about this, the list of files available entirely depends on the kernel and what's namespace aware in the Linux kernel.