af_iucv: New error return codes for connect()

af_iucv: New error return codes for connect()

If the iucv_path_connect() call fails then return an error code that
corresponds to the iucv_path_connect() failure condition; instead of
returning -ECONNREFUSED for any failure.

This helps to improve error handling for user space applications
(e.g.  inform the user that the z/VM guest is not authorized to
connect to other guest virtual machines).

The error return codes are based on those described in connect(2).

Signed-off-by: Hendrik Brueckner <[email protected]>
Signed-off-by: Ursula Braun <[email protected]>
Signed-off-by: David S. Miller <[email protected]>