qemu-iotests: add initial tests for live block commit
Derived from the streaming test cases (030), this adds the
following 9 tests:
1. For the following image chain, commit [mid] into [backing],
and use qemu-io to verify [backing] has its original data, as
well as the data from [mid]
[backing] <-- [mid] <-- [test]
2. Verifies that 'block-commit' with the 'speed' parameter sets the
speed parameter, as reported by 'query-block-jobs'
3. Verifies that a bogus 'device' parameter to 'block-commit'
results in error
4-9: Appropriate error values returned for the following argument errors:
* top == base
* top is nonexistent
* base is nonexistent
* top == active layer (this is currently not supported)
* top and base arguments are reversed
* top argument is omitted
Signed-off-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>