Don't leak memory in remove_from_boot_order()

Signed-off-by: Peter Jones <pjones@redhat.com>
Fix some leaked memory that shows up in valgrind.

Signed-off-by: Peter Jones <pjones@redhat.com>
Add the ability to clean up duplicates in BootOrder

This adds -D (--remove-dups), which iterates BootOrder and keeps only
the first of any number it finds.  Duplicate entries can happen as a
result of an interaction between fallback.efi and some system firmware,
and this option provides an easy workaround to fix it.

Resolves: rhbz#1097396

Signed-off-by: Peter Jones <pjones@redhat.com>