LU-13736 lnet: Do not set preferred NI for MR peer

LU-13736 lnet: Do not set preferred NI for MR peer

The preferred NI exists to ensure that a consistent source address is
used when communicating with a non-multi-rail peer. We needn't ever
set a preferred NI for a MR peer.

HPE-bug-id: LUS-9058
Signed-off-by: Chris Horn <chris.horn@hpe.com>
Change-Id: I836a314dbf02d35199c3da2ccea6fb0acbb94b54
Reviewed-on: https://review.whamcloud.com/39229
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Oleg Drokin <green@whamcloud.com>