iscsi,iser-target: Expose supported protection ops according to t10_pi
iSER will report supported protection operations based on
the tpg attribute t10_pi settings and HCA PI offload capabilities.
If the HCA does not support PI offload or tpg attribute t10_pi is
not set, we fall to SW PI mode.
In order to do that, we move iscsit_get_sup_prot_ops after connection
tpg assignment.