LU-11422 lnet: Fix selftest backward compatibility post health

LU-11422 lnet: Fix selftest backward compatibility post health

Post LNet health feature landing, lnet-selftest loses
backward compatibility. This patch fixes that by
adding a new structure lnet_counters_common similar
to lnet_counters(pre-Health version). Now,
lnet_counters_common is the struct that selftest depends on.

Also, adds a struct lnet_counters_health specifically
for health stats.

Change-Id: Ia066ff7b3522738080d192e80c14cf5ac55a33e2
Test-Parameters: trivial testlist=lnet-selftest clientjob=lustre-b2_10 clientbuildno=136
Signed-off-by: Sonia Sharma <sharmaso@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/33242
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Amir Shehata <ashehata@whamcloud.com>
Tested-by: Jenkins
Tested-by: Andreas Dilger <adilger@whamcloud.com>