platform: resynchronize with kernel when we're out of buffer space

Kernel can return ENOBUFS in variety of reasons. If that happens, we know we've
lost events and should pick up kernel state.

Simple reproducer that triggers an ENOBUFS condition no matter how big our
netlink socket buffer is:

  ip link add bridge0 type bridge
  for i in seq $(0 1023); do ip link add dummy$i type dummy; \
    ip link set dummy$i master bridge0; done
  ip link del bridge0
Revert "platform: increase NL buffer for systems with lots of interfaces (rh #1141256)"

This reverts commit efd09845c41e08469d6f6bffa23bd90b6bd06e85.

It turns out that the socket space might not be the only buffer that may get
too full. 128K ought to be enough for it and we should resynchronize with the
kernel now if needed.
device: release and enslave an interface if its master changed

In case of an atomic master change, we'd not notice that the master changed:

  ip link set dummy0 master bridge0
  ip link set dummy0 master bridge1
device: set the master on device addition

Otherwise we won't notice the device is a slave on NM startup until someone
changes the link or tries to activate the device.
device: assume connections for device with slaves

If a bridge/team/bond has slaves, assume it's connected. Recheck as devices
appear.

https://bugzilla.redhat.com/show_bug.cgi?id=1141266
Merge remote-tracking branches 'fd/lr/veth-managed', 'fd/lr/no-udev', 'fd/lr/vpn-fixes' and 'fd/lr/bridge-rh1141266' into integration