[SCSI] iscsi_tcp: Evaluate socket state in data_ready()

The network core will call the state_change() callback
prior to the data_ready() callback, which might cause
us to lose a connection state change.
So we have to evaluate the socket state at the end
of the data_ready() callback, too.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>