LU-9933 lnet: Handle ping buffer with only loopback NID

LU-9933 lnet: Handle ping buffer with only loopback NID

During startup lnet_peer_data_resent() can see a ping buffer
for the local node which contains only the loopback NID. This
shows up as pi_nnis == 1, and there is nothing to be done (or
that needs to be done) in that case.

Signed-off-by: Olaf Weber <olaf.weber@hpe.com>
Change-Id: Ie5454b58f01ded17d0cff47ad5358e5d4bcebcd8
Reviewed-on: https://review.whamcloud.com/28811
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Amir Shehata <amir.shehata@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>