iscsi: Set bs->request_alignment

The iSCSI backend already gets the block size from the READ CAPACITY
command it sends.  Save it so that the generic block layer gets it
too.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>

block/iscsi.c

@@ -1217,6 +1217,7 @@ static int iscsi_open(BlockDriverState *bs, QDict *options, int flags,
         goto out;
     }
     bs->total_sectors = sector_lun2qemu(iscsilun->num_blocks, iscsilun);
+    bs->request_alignment = iscsilun->block_size;
 
     /* Medium changer or tape. We dont have any emulation for this so this must
      * be sg ioctl compatible. We force it to be sg, otherwise qemu will try