[SCSI] qla2xxx: Use proper HA during asynchrounous event handling.

Changes are added to the driver so that it can behave properly
upon having asynchronous events, for example, addition of target
devices to the VPs.

Signed-off-by: Seokmann Ju <seokmann.ju@qlogic.com>
Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>