Merge remote-tracking branch 'remotes/famz/tags/staging-pull-request' into staging

Block and testing patches

- Paolo's AIO fixes.
- VMDK streamOptimized corner case fix
- VM testing improvment on -cpu

# gpg: Signature made Wed 26 Sep 2018 03:54:08 BST
# gpg:                using RSA key CA35624C6A9171C6
# gpg: Good signature from "Fam Zheng <[email protected]>"
# Primary key fingerprint: 5003 7CB7 9706 0F76 F021  AD56 CA35 624C 6A91 71C6

* remotes/famz/tags/staging-pull-request:
  vmdk: align end of file to a sector boundary
  tests/vm: Use -cpu max rather than -cpu host
  aio-posix: do skip system call if ctx->notifier polling succeeds
  aio-posix: compute timeout before polling
  aio-posix: fix concurrent access to poll_disable_cnt

Signed-off-by: Peter Maydell <[email protected]>