[SCSI] ibmvfc: Add ADISC support

Add an ADISC to the target discovery job in order to sanity check whether or
not we need to re-login to the target.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>