Fix prio vs. nonprio tagged traffic in RDMACM

In current RDMACM implementation RDMACM server will not find a GID
index when the request was prio-tagged and the sever is non
prio-tagged and vise-versa.
According to 802.1Q-2014, VLAN tagged packets with VLAN id 0 should
be considered as untagged. Treat RDMACM request the same.

Reviewed by: hselasky, kib
MFC after: 3 Days
Sponsored by: Mellanox Technologies