Merge remote-tracking branch 'kwolf/for-anthony' into staging

* kwolf/for-anthony:
  qemu-iotests: skip 039 with ./check -nocache
  block: add BLOCK_O_CHECK for qemu-img check
  qcow2: mark image clean after repair succeeds
  qed: mark image clean after repair succeeds
  blockdev: flip default cache mode from writethrough to writeback
  virtio-blk: disable write cache if not negotiated
  virtio-blk: support VIRTIO_BLK_F_CONFIG_WCE
  qemu-iotests: Save some sed processes
  ahci: Fix sglist memleak in ahci_dma_rw_buf()
  ahci: Fix ahci cdrom read corruptions for reads > 128k
  virtio-blk: fix use-after-free while handling scsi commands