Fix storage cleanup corner case preventing VM deletion (apache#5575)

* Fix storage cleanup corner case

* Improve deletion

* Refactor

Author: nvazquez

engine/storage/volume/src/main/java/org/apache/cloudstack/storage/volume/VolumeServiceImpl.java

@@ -1510,6 +1510,7 @@ protected Void copyVolumeCallBack(AsyncCallbackDispatcher<VolumeServiceImpl, Cop
                 srcVolume.processEvent(Event.OperationSuccessed);
                 destVolume.processEvent(Event.MigrationCopySucceeded, result.getAnswer());
                 volDao.updateUuid(srcVolume.getId(), destVolume.getId());
+                volDao.detachVolume(srcVolume.getId());
                 try {
                     destroyVolume(srcVolume.getId());
                     srcVolume = volFactory.getVolume(srcVolume.getId());