Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2019-09-16' into staging

Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2019-09-16' into staging

Block patches:
- Fix for block jobs when used with I/O threads
- Fix for a corruption when using qcow2's LUKS encryption mode
- cURL fix
- check-block.sh cleanups (for make check)
- Refactoring

# gpg: Signature made Mon 16 Sep 2019 14:41:15 BST
# gpg:                using RSA key 91BEB60A30DB3E8857D11829F407DB0061D5CF40
# gpg:                issuer "mreitz@redhat.com"
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>" [full]
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* remotes/maxreitz/tags/pull-block-2019-09-16:
  qemu-iotests: Add test for bz #1745922
  block/qcow2: refactor encryption code
  block/qcow2: Fix corruption introduced by commit 8ac0f15f335
  blockjob: update nodes head while removing all bdrv
  curl: Check curl_multi_add_handle()'s return code
  curl: Handle success in multi_check_completion
  curl: Report only ready sockets
  curl: Pass CURLSocket to curl_multi_do()
  curl: Check completion in curl_multi_do()
  curl: Keep *socket until the end of curl_sock_cb()
  curl: Keep pointer to the CURLState in CURLSocket
  tests/qemu-iotests: Fix qemu-io related output in 026.out.nocache
  tests/Makefile: Do not print the name of the check-block.sh shell script
  tests/qemu-iotests/check: Replace "tests" with "iotests" in final status text
  block: Remove unused masks
  block: Use QEMU_IS_ALIGNED

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