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

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

# gpg: Signature made Mon 29 Feb 2016 20:08:16 GMT using RSA key ID C0DE3057
# gpg: Good signature from "Jeffrey Cody <[email protected]>"
# gpg:                 aka "Jeffrey Cody <[email protected]>"
# gpg:                 aka "Jeffrey Cody <[email protected]>"

* remotes/cody/tags/block-pull-request:
  iotests/124: Add cluster_size mismatch test
  block/backup: avoid copying less than full target clusters
  block/backup: make backup cluster size configurable
  mirror: Add mirror_wait_for_io
  mirror: Rewrite mirror_iteration
  vhdx: Simplify vhdx_set_shift_bits()
  vhdx: DIV_ROUND_UP() in vhdx_calc_bat_entries()
  iscsi: add support for getting CHAP password via QCryptoSecret API
  curl: add support for HTTP authentication parameters
  rbd: add support for getting password from QCryptoSecret object
  sheepdog: allow to delete snapshot
  block/nfs: add support for setting debug level

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