Merge remote-tracking branch 'remotes/xanclic/tags/pull-block-2019-01-31' into staging

Merge remote-tracking branch 'remotes/xanclic/tags/pull-block-2019-01-31' into staging

Block patches:
- New debugging QMP command to explore block graphs
- Converted DPRINTF()s to trace events
- Fixed qemu-io's use of getopt() for systems with optreset
- Minor NVMe emulation fixes
- An iotest fix

# gpg: Signature made Thu 31 Jan 2019 00:51:46 GMT
# gpg:                using RSA key F407DB0061D5CF40
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>" [full]
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* remotes/xanclic/tags/pull-block-2019-01-31:
  iotests: Allow 147 to be run concurrently
  iotests: Bind qemu-nbd to localhost in 147
  iotests.py: Add qemu_nbd_pipe()
  nvme: use pci_dev directly in nvme_realize
  nvme: ensure the num_queues is not zero
  nvme: use TYPE_NVME instead of constant string
  qemu-io: Add generic function for reinitializing optind.
  block/sheepdog: Convert from DPRINTF() macro to trace events
  block/file-posix: Convert from DPRINTF() macro to trace events
  block/curl: Convert from DPRINTF() macro to trace events
  block/ssh: Convert from DPRINTF() macro to trace events
  scripts: add render_block_graph function for QEMUMachine
  qapi: add x-debug-query-block-graph

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