scsi: qla2xxx: Prevent relogin trigger from sending too many commands

This patch adds check for pending work event before queueing
relogin work to prevent redundant work to be active at the
same time.

Signed-off-by: Quinn Tran <quinn.tran@cavium.com>
Signed-off-by: Himanshu Madhani <himanshu.madhani@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>