LU-15102 lnet: Reset ni_ping_count only on receive

The lnet_ni:ni_ping_count is currently reset on every (healthy) tx.
We should only reset it when receiving a message over the NI. Taking
net_lock 0 on every tx results in a performance loss for certain
workloads.

Test-Parameters: trivial testlist=sanity-lnet
Fixes: 8fdf2bc62a ("LU-13569 lnet: Recover local NI w/exponential backoff interval")
HPE-bug-id: LUS-10427
Signed-off-by: Chris Horn <chris.horn@hpe.com>
Change-Id: I67ea3aa977cb5d67b04f7957120c29e9985c83e6
Reviewed-on: https://review.whamcloud.com/45235
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Andriy Skulysh <andriy.skulysh@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>