netlink: remove use of libnl3

netlink: remove use of libnl3

Use netlink implementation from 0.7.19 instead but manage a cache
ourselves. The changes are quite minimal compared to the implementation
in 0.7.19. We handle deletion and updates. The use of linked list may be
problematic performance-wise.

When an interface goes down then up, no PDU is scheduled to be sent
again. This bug was already present in the previous implementation and
should be a regression of 36080c.