Add test cases for merging various pairs of bitmaps when snapshots were
created together with checkpoints.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

Add all intermediate steps and deletion of the current checkpoint on a
flat (single-image) disk image.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>