Add a before and after etc/default/grub for grub2 testing

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
grub2: allow both /etc/default/grub and the grub.cfg glob to be specified during test

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
grub2: always specify the desired kernel by label rather than digit

Although the user initially selected by digit, switch to a "name"
label since it's more explicit.

Also the digit never worked for me.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Merge pull request #40 from djs55/grub2

grub2: always name the kernel rather than using the digit