Revert "Merge branch 'CA-147671' into xs64bit"

This reverts commit e1d4b6a5b5e2990e37c30e6189eeffbc89fe729e, reversing
changes made to 8c43c80de28b6911b96822048de3cf27752bb553.

Commits 5b23740c and 0d146e6b are reverted because they break the build
and the merge doesn't have a "GitHub: closes ..." tag.

Signed-off-by: Thanos Makatos <thanos.makatos@citrix.com>
CA-147671: Refactor block-aio.c before unit testing tdaio_queue_read

Signed-off-by: Flavien Quesnel <flavien.quesnel@citrix.com>
Reviewed-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@citrix.com>
CA-147671: [UnitTest] Add unit tests for tdaio_queue_read

Signed-off-by: Flavien Quesnel <flavien.quesnel@citrix.com>
Reviewed-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>
Merge branch 'CA-147671' into xs64bit

Signed-off-by: Flavien Quesnel <flavien.quesnel@citrix.com>

GitHub: closes #137 on xapi-project/blktap