LU-11551 lnet: Do not allow deleting of router nis

LU-11551 lnet: Do not allow deleting of router nis

Check the peer before deleting a peer_ni. If it's a router then do
not allow deletion of the peer-ni.

Test-Parameters: forbuildonly
Signed-off-by: Amir Shehata <ashehata@whamcloud.com>
Change-Id: I372052b4e9b5af3a8f18a49676fc60b4c8077cbd
Reviewed-on: https://review.whamcloud.com/33448
Reviewed-by: Olaf Weber <olaf.weber@hpe.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Chris Horn <hornc@cray.com>
Tested-by: Jenkins