ipvs: More reliable synchronization on connection close

This patch enhances the synchronization of the closing connections
between the master and the backup director. It prevents the closed
connections to expire with the 15 min timeout of the ESTABLISHED
state on the backup and makes them expire as they would do on the
master with much shorter timeouts.

Signed-off-by: Rumen G. Bogdanovski <rumen@voicecho.com>
Acked-by: Simon Horman <horms@verge.net.au>
Signed-off-by: David S. Miller <davem@davemloft.net>