[SCSI] qla4xxx: Quiesce driver activities while loopback

Quiesce all different activities performed by driver upon the link events
while loopback diagnostics is in progress.

Signed-off-by: Nilesh Javali <nilesh.javali@qlogic.com>
Signed-off-by: Vikas Chaudhary <vikas.chaudhary@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>