Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches for 2.6

# gpg: Signature made Tue 12 Apr 2016 17:10:29 BST using RSA key ID C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"

* remotes/kevin/tags/for-upstream:
  qemu-iotests: iotests.py: get rid of __all__
  qemu-iotests: 068: don't require KVM
  qemu-iotests: 148: properly skip test if quorum support is missing
  qemu-iotests: iotests.VM: remove qtest socket on error
  qemu-iotests: fix 051 on non-PC architectures
  qemu-iotests: check: don't place files with predictable names in /tmp
  MAINTAINERS: Block layer core, qcow2 and blkdebug
  qcow2: Prevent backing file names longer than 1023
  vpc: fix return value check for blk_pwrite
  iotests: Make 150 use qemu-img map instead of du
  block: initialize qcrypto API at startup
  qemu-img: fix formatting of error message
  iotests: fix the broken 026.nocache output

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>