LU-447 lnet: add lctl --net XXX push

LU-447 lnet: add lctl --net XXX push

Lctl --net XXX push is used to clear out purgatory conns arbitrarily.
We use this with lctl --net XXX disconnect for regression testing.
This does not nuke the peer, so it shouldn't yield lnd_query failures
like del_peer does.

Signed-off-by: James Simmons <uja.ornl@gmail.com>
Signed-off-by: Bob Glossman <bogl@whamcloud.com>
Change-Id: Ia7b033750134020022df676f451d91b20e4f5db4
Reviewed-on: http://review.whamcloud.com/2645
Reviewed-by: Lai Siyao <laisiyao@whamcloud.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>