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.

Change-Id: Ib47bde4497b8ef49deb6bbfa0c4d8f5b40470c5e
Signed-off-by: James Simmons <uja.ornl@gmail.com>
Reviewed-on: http://review.whamcloud.com/1003
Reviewed-by: Cory Spitz <spitzcor@cray.com>
Tested-by: Hudson
Reviewed-by: Lai Siyao <laisiyao@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>