LU-13896 lnet: Fix reference leak in lnet_select_pathway

LU-13896 lnet: Fix reference leak in lnet_select_pathway

We call lnet_nid2peerni_locked() to lookup the peer NI for the message
originator. lnet_nid2peerni_locked() takes a reference on the peer NI
that is never dropped.

Test-Parameters: trivial
Fixes: b0e8ab1a5f ("LU-13606 lnet: Allow router to forward to healthier NID")
HPE-bug-id: LUS-9185
Signed-off-by: Chris Horn <chris.horn@hpe.com>
Change-Id: Ie0e8f215d7becfbf33f905a1806da8513798ee8d
Reviewed-on: https://review.whamcloud.com/39603
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Amir Shehata <ashehata@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>