LU-12279 lnet: use number of wrs to calculate CQEs

LU-12279 lnet: use number of wrs to calculate CQEs

Using concurrent sends to calculate the number of CQEs results
in a small number of CQEs which exposes an issue where under
failure scenarios, example when a node reboots, there wouldn't
be enough CQEs available leading to IB_EVENT_QP_FATAL

Fixes: 83e45ead69ba ("LU-11931 lnd: bring back concurrent_sends")
Signed-off-by: Amir Shehata <ashehata@whamcloud.com>
Change-Id: I6e2be079e11622b83fe3fb4fdb695f5a2672c9ac
Reviewed-on: https://review.whamcloud.com/34945
Tested-by: Jenkins
Reviewed-by: Sonia Sharma <sharmaso@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>