linux-cp: resync with kernel after nl socket error

linux-cp: resync with kernel after nl socket error

Type: improvement

Currently, if an error happens on the netlink notification socket, the
socket gets reopened. A portion of notification messages have been lost
because of this and will never arrive on the socket. VPP will be out of
sync with the kernel networking state.

With this change, synchronize VPP state and the kernel networking state
if there was an error polling or reading the notification socket.

Signed-off-by: Alexander Chernavin <[email protected]>
Change-Id: I8cdff89b505cd227535a0acaadb6ee757204c45e