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

Pull request

Rebase notes:

011/36:[0003] [FC] 'block/backup: upgrade copy_bitmap to BdrvDirtyBitmap'
016/36:[----] [-C] 'iotests: Add virtio-scsi device helper'
017/36:[0002] [FC] 'iotests: add test 257 for bitmap-mode backups'
030/36:[0011] [FC] 'block/backup: teach TOP to never copy unallocated regions'
032/36:[0018] [FC] 'iotests/257: test traditional sync modes'

11: A new hbitmap call was added late in 4.1, changed to
    bdrv_dirty_bitmap_next_zero.
16: Context-only (self.has_quit is new context in 040)
17: Removed 'auto' to follow upstream trends in iotest fashion
30: Handled explicitly on-list with R-B from Max.
32: Fix capitalization in test, as mentioned on-list.

# gpg: Signature made Sat 17 Aug 2019 00:12:13 BST
# gpg:                using RSA key F9B7ABDBBCACDF95BE76CBD07DEF8106AAFC390E
# gpg: Good signature from "John Snow (John Huston) <[email protected]>" [full]
# Primary key fingerprint: FAEB 9711 A12C F475 812F  18F2 88A9 064D 1835 61EB
#      Subkey fingerprint: F9B7 ABDB BCAC DF95 BE76  CBD0 7DEF 8106 AAFC 390E

* remotes/jnsnow/tags/bitmaps-pull-request: (36 commits)
  tests/test-hbitmap: test next_zero and _next_dirty_area after truncate
  block/backup: refactor write_flags
  block/backup: deal with zero detection
  qapi: add dirty-bitmaps to query-named-block-nodes result
  iotests/257: test traditional sync modes
  block/backup: support bitmap sync modes for non-bitmap backups
  block/backup: teach TOP to never copy unallocated regions
  block/backup: add backup_is_cluster_allocated
  block/backup: centralize copy_bitmap initialization
  block/backup: improve sync=bitmap work estimates
  iotests/257: test API failures
  block/backup: hoist bitmap check into QMP interface
  iotests/257: Refactor backup helpers
  iotests/257: add EmulatedBitmap class
  iotests/257: add Pattern class
  iotests: test bitmap moving inside 254
  qapi: implement block-dirty-bitmap-remove transaction action
  blockdev: reduce aio_context locked sections in bitmap add/remove
  block/backup: loosen restriction on readonly bitmaps
  iotests: add test 257 for bitmap-mode backups
  ...

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