core: do not use dirty extents for full backup

Currently the code checks if the backup is incremental, however if the
disk is RAW the client will defer to full backup instead and only incremental
backup supports dirty extents.

This patch considers the mode of the backup when deciding whether use
dirty extents.

Bug-Url: https://bugzilla.redhat.com/2068104
Signed-off-by: Benny Zlotnik <bzlotnik@redhat.com>

backend/manager/modules/bll/src/main/java/org/ovirt/engine/core/bll/storage/disk/image/TransferDiskImageCommand.java

@@ -1209,7 +1209,9 @@ private boolean isHybridBackup() {
     }
 
     private boolean isSupportsDirtyExtents() {
-        if (!isBackup() || getParameters().getTransferType() != TransferType.Download) {
+        if (!isBackup() ||
+                getParameters().getTransferType() != TransferType.Download ||
+                getDiskImage().getBackupMode() != DiskBackupMode.Incremental) {
             return false;
         }
         VmBackup backup = getBackup();