The xprtrdma connect logic can return -EPROTO if the underlying
device or network path does not support RDMA. This can happen
after a device removal/insertion.

- When SOFTCONN is set, EPROTO is a permanent error.

- When SOFTCONN is not set, EPROTO is treated as a temporary error.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>