grubby-bls: make a copy of the cmdline if is modified for an entry
The BLS entries use a global kernel command line parameters that's set as
kernelopts variable in the grubenv file. But users may want to have custom
parameters for some entries, so make a copy of the current kernelopts and
set the "options" field value to the modified parameters.
Resolves: rhbz#1629054
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>