scsi: qedf: Stop sending fipvlan request on unload

 - On some setups fipvlan can be retried for long duration and the
   connection to switch was not there so it was not getting any reply.

 - During unload this thread was hanging.

Problem Resolution:

Check if unload is in progress, then quit from fipvlan thread.

Signed-off-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>