qemu: Block blockjobs when transient disk option is enabled

For now we disallow blockjobs with transient disks to avoid dealing with
obsoleted overlays.

Signed-off-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Tested-by: Ján Tomko <jtomko@redhat.com>

src/qemu/qemu_domain.c

@@ -10859,6 +10859,13 @@ qemuDomainDiskBlockJobIsSupported(virDomainObjPtr vm,
         return false;
     }
 
+    if (disk->transient) {
+        virReportError(VIR_ERR_OPERATION_UNSUPPORTED,
+                       _("block jobs are not supported on transient disk '%s'"),
+                       disk->dst);
+        return false;
+    }
+
     return true;
 }