Fix the grub2 backup template

Missing an equals sign. Grub2 doesn't like it.

Change-Id: Ia77742fda7af2ee881950ae756f939227659bfb3
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1150868
Signed-off-by: Ryan Barry <rbarry@redhat.com>