LU-14668 lnet: Lock primary NID logic

LU-14668 lnet: Lock primary NID logic

If a peer is created by Lustre make sure to lock that peer's
primary NID. This peer can be discovered in the background.
There is no need to block until discovery is complete, as Lustre
can continue on with the primary NID it provided.

Discovery will populate the peer with other interfaces the peer has
but will not change the peer's primary NID. It can also delete
peer's NIDs which Lustre told it about (not the Primary NID).

Signed-off-by: Amir Shehata <ashehata@whamcloud.com>
Change-Id: I677b8e01fc89a42128327645861ca6cfba4c1b1a
Reviewed-on: https://review.whamcloud.com/43563
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>