LU-13028 lnet: advertise discovery when toggled

LU-13028 lnet: advertise discovery when toggled

When discovery is toggled send a push message to all peers.
When a node receives a push notification that discovery is
turned off while previously it was on, then delete the peer
information. If the peer is a router, recreate the routes.

Test-parameters: trivial

Signed-off-by: Amir Shehata <ashehata@whamcloud.com>
Change-Id: I58f9f42542e4c05763128d7c9d23108c3e7f13a3
Reviewed-on: https://review.whamcloud.com/36919
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>