When running in the AWSVPC mode, we need to do the following:
- Keep the HW TX offloading on.
- Check that the allocated address belongs to the default subnet,
because only one subnet is allowed and it should be the default one.
If it is not possible to determine whether AWSVPC is on, we ignore
all the steps, because the attachment routines have to work
regardless whether the router is running and the AWSVPC detection
is done by querying the /ipinfo/tracker endpoint served by
the router.
Also move netlink and netns code from common to net
Creates interface if not already there
Adds addresses
Move the set link 'up' to after addresses are added
Martynas Pumputis