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

Block layer patches:

- Relax restrictions for blockdev-snapshot (allows libvirt to do live
  storage migration with blockdev-mirror)
- luks: Delete created files when block_crypto_co_create_opts_luks fails
- Fix memleaks in qmp_object_add

# gpg: Signature made Wed 11 Mar 2020 15:38:59 GMT
# gpg:                using RSA key 7F09B272C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>" [full]
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream:
  qemu-iotests: adding LUKS cleanup for non-UTF8 secret error
  crypto.c: cleanup created file when block_crypto_co_create_opts_luks fails
  block.c: adding bdrv_co_delete_file
  block: introducing 'bdrv_co_delete_file' interface
  tests/qemu-iotests: Fix socket_scm_helper build path
  qapi: Add '@allow-write-only-overlay' feature for 'blockdev-snapshot'
  iotests: Add iothread cases to 155
  block: Fix cross-AioContext blockdev-snapshot
  iotests: Test mirror with temporarily disabled target backing file
  iotests: Fix run_job() with use_log=False
  block: Relax restrictions for blockdev-snapshot
  block: Make bdrv_get_cumulative_perm() public
  qom-qmp-cmds: fix two memleaks in qmp_object_add

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

diff --cc block/crypto.c
Simple merge

diff --cc tests/qemu-iotests/group
Simple merge

diff --cc tests/qtest/Makefile.include
Simple merge