[SCSI] qla4xxx: fix host reset dpc race

The host reset callout could be starting to reset the hba at the same
time the dpc thread is. This creates lots of problems because they both
want to do wierd things with the firmware and interrupts, etc.

This patch just has the host reset function fully shutdown the dpc
thread before resetting the hba.

This patch also moves the setting of the session online bit to fix
a potential race with the dpc thread and iscsi recovery thread.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Acked-by: David C Somayajulu <david.somayajulu@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>