Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2017-04-11' into staging

Block patches for 2.9.0-rc4

# gpg: Signature made Tue 11 Apr 2017 14:40:07 BST
# gpg:                using RSA key 0xF407DB0061D5CF40
# gpg: Good signature from "Max Reitz <[email protected]>"
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* remotes/maxreitz/tags/pull-block-2017-04-11:
  iscsi: Fix iscsi_create
  throttle: Remove block from group on hot-unplug
  block: pass the right options for BlockDriver.bdrv_open()

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