lpfc: Devices are not discovered during takeaway/giveback testing

When a remote nport changes it's DID, a new ndlp is used.
However, we left the old ndlp state unchanged and still in
a discovery state. The may stall discovery resulting in some
devices not being discovered.  Correct by swapping the state
of the 2 ndlp's when a DID swap is detected.

Signed-off-by: Dick Kennedy <dick.kennedy@avagotech.com>
Signed-off-by: James Smart <james.smart@avagotech.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: James Bottomley <JBottomley@Odin.com>