Reference: bnc#885094
grub.xen is required to boot Xen PV VMs using BTRFS. It belongs to
the grub2-x86_64-xen RPM and should never be deleted.
Index: virt-manager-3.3.0/virtManager/delete.py
===================================================================
--- virt-manager-3.3.0.orig/virtManager/delete.py
+++ virt-manager-3.3.0/virtManager/delete.py
@@ -459,7 +459,7 @@ def _populate_storage_list(storage_list,
     model.clear()
 
     for diskdata in diskdatas:
-        if not diskdata.path:
+        if not diskdata.path or diskdata.path == "/usr/lib/grub2/x86_64-xen/grub.xen":
             continue
 
         # There are a few pieces here