EFI changes for EL7

Grub is grubx64 now instead of just grub, and partitions in
/dev/mapper don't always use p(\d+), so efibootmgr will try to
install on a partition if the regex isn't changed. This probably
also affects Fedora

Change-Id: I50f16b95c65c874f95dbd02033136dff83bac856
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1130965
Signed-off-by: Ryan Barry <rbarry@redhat.com>