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

# gpg: Signature made Tue 16 May 2017 04:47:09 PM BST
# gpg:                using RSA key 0xBDBE7B27C0DE3057
# gpg: Good signature from "Jeffrey Cody <jcody@redhat.com>"
# gpg:                 aka "Jeffrey Cody <jeff@codyprime.org>"
# gpg:                 aka "Jeffrey Cody <codyprime@gmail.com>"
# Primary key fingerprint: 9957 4B4D 3474 90E7 9D98  D624 BDBE 7B27 C0DE 3057

* jtc/tags/block-pull-request:
  curl: do not do aio_poll when waiting for a free CURLState
  curl: convert readv to coroutines
  curl: convert CURLAIOCB to byte values
  curl: split curl_find_state/curl_init_state
  curl: avoid recursive locking of BDRVCURLState mutex
  curl: never invoke callbacks with s->mutex held
  curl: strengthen assertion in curl_clean_state
  block: curl: Allow passing cookies via QCryptoSecret

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>