Merge remote-tracking branch 'mreitz/tags/pull-block-for-kevin-2015-12-18' into queue-block

block-next patches from before the 2.5.0 release.

# gpg: Signature made Fri Dec 18 14:38:44 2015 CET using RSA key ID E838ACAD
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>"

* mreitz/tags/pull-block-for-kevin-2015-12-18:
  block/qapi: allow best-effort query
  qemu-img: abort when full_backing_filename not present
  block/qapi: explicitly warn if !has_full_backing_filename
  block/qapi: always report full_backing_filename
  block/qapi: do not redundantly print "actual path"
  qemu-iotests: s390x: fix test 068
  qemu-iotests: s390x: fix test 051
  qemu-iotests: refine common.config

Signed-off-by: Kevin Wolf <kwolf@redhat.com>