Protect NPL lists with host lock

Symptoms: lpfc_findnode_rpi and lpfc_findnode_did can be called
outside of the discovery thread context. We have to iterate
through the NPL lists under the host lock and all add/del
operations on those lists have to be done under host lock.
Signed-off-by: Jamie Wellnitz <Jamie.Wellnitz@emulex.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>