failed to modify QP to RTR for RoCEv2

[liaoyunkun]

Hi, your work is pretty good. I encountered "failed to modify QP to RTR" bug in my RoCEv2 environment. I found that the bug is due to the missing of "sgid_index" in the configuration of GRH.
I fix the bug by adding attr.ah_attr.grh.sgid_index = user_param.gid_index(if RoCE) in the pp_connect_ctx function.

Moreover, Yiwen, I plan to solve the performance isolation problem from the internal architecture of RDMA NIC. Could you please provide some insights? :-)