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-1.3.0/virtManager/delete.py
===================================================================
--- virt-manager-1.3.0.orig/virtManager/delete.py
+++ virt-manager-1.3.0/virtManager/delete.py
@@ -242,7 +242,7 @@ def populate_storage_list(storage_list,
     diskdata.append(("dtb", vm.get_xmlobj().os.dtb, True, False))
 
     for target, path, ro, shared in diskdata:
-        if not path:
+        if not path or path == "/usr/lib/grub2/x86_64-xen/grub.xen":
             continue
 
         # There are a few pieces here