xen/blkback: Fix the WRITE_BARRIER

The WRITE_BARRIER was missing the REQ_WRITE option. This
was causing the blktap to die.

Signed-off-by: Tom Goetz <tom.goetz@virtualcomputer.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
1 file changed