[SCSI] ibmvfc: Ignore fabric RSCNs when link is dead

This fixes an issues seen where a Fabric RSCN event was received
while the link was down, which resulted in repeated attempts to log back
into the fabric, which then failed, resulting in the ibmvfc driver
taking the host offline. Fix this by delaying taking any action
regarding the fabric RSCN until the link comes back up.

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