Unbreak grub for precise.
Unbreak grub for precise.

Change-Id: I5739b95e08c25d732223ad36d00aa1a46f67ff28

JioCloud/diskimage-builder,eantyshev/diskimage-builder,varunarya10/diskimage-builder,citrix-openstack-build/diskimage-builder,rdo-management/diskimage-builder,eantyshev/diskimage-builder,citrix-openstack-build/diskimage-builder,openstack/diskimage-builder,zioproto/diskimage-builder,takahashinobuyuki/diskimage-builder,openstack/diskimage-builder,switch-ch/diskimage-builder,switch-ch/diskimage-builder,rdo-management/diskimage-builder,CSC-IT-Center-for-Science/diskimage-builder,NaohiroTamura/diskimage-builder,takahashinobuyuki/diskimage-builder,CSC-IT-Center-for-Science/diskimage-builder,NaohiroTamura/diskimage-builder,varunarya10/diskimage-builder,zioproto/diskimage-builder,JioCloud/diskimage-builder