[SCSI] qla2xxx: Stall mid-layer error handlers while rport is blocked.

Stall error handler if attempting recovery while an rport is
blocked.  This avoids device offline scenarios due to errors in
the error handler.

Reference implementation from lpfc/mptfc.

Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>