qemublocktest: Add tests for re-enabling of bitmaps after commit

qemublocktest: Add tests for re-enabling of bitmaps after commit

Some branches were not covered and thus we didn't catch that the bitmaps
are not re-enabled if nothing is merged into them. Two bitmaps are
necessary to reliably test the case due to hash table ordering.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Tested-by: Daniel P. Berrangé <berrange@redhat.com>