server: fix VM with ISO attached migration issue (#3935)

As previously described by PR #3929:
If vm has attached ISO, the migration fails with error message "org.libvirt.LibvirtException: Cannot access storage file /mnt/b33e5a1d-e4ea-3465-b6ac-c98dc8ff8af0/207-2-cc5fd717-2d57-3bb3-bcf6-2c930268db6c.iso"

Author: nvazquez

engine/storage/image/src/main/java/org/apache/cloudstack/storage/image/TemplateDataFactoryImpl.java

@@ -68,7 +68,7 @@ public class TemplateDataFactoryImpl implements TemplateDataFactory {
     @Override
     public TemplateInfo getTemplate(long templateId, DataStore store) {
         VMTemplateVO templ = imageDataDao.findById(templateId);
-        if (store == null) {
+        if (store == null && !templ.isDirectDownload()) {
             TemplateObject tmpl = TemplateObject.getTemplate(templ, null);
             return tmpl;
         }

server/src/main/java/com/cloud/template/TemplateManagerImpl.java

@@ -584,10 +584,8 @@ public void prepareIsoForVmProfile(VirtualMachineProfile profile, DeployDestinat
                     }
                     poolId = storagePool.getId();
                 }
-                template = prepareIso(vm.getIsoId(), vm.getDataCenterId(), dest.getHost().getId(), poolId);
-            } else {
-                template = _tmplFactory.getTemplate(vm.getIsoId(), DataStoreRole.Primary, dest.getDataCenter().getId());
             }
+            template = prepareIso(vm.getIsoId(), vm.getDataCenterId(), dest.getHost().getId(), poolId);
 
             if (template == null){
                 s_logger.error("Failed to prepare ISO on secondary or cache storage");