Add grub menu.lst to the ramdisk image

Xen-based systems booting in paravirt mode require a grub menu.lst file
be present in the image for pvgrub to read.

Non-xen images will still use the embedded grub. Note, however, that the
internal grub does NOT use the menu.lst but instead uses a hard coded
string in external/grub/stage2/preset_menu.c. For it to use a menu.lst
file in the filesystem we would need to add a stage1_5 image for ext2,
which is left as an exercise for the reader.

Change-Id: I1cad489118c1757b94a72d50915c7e5644b0df17
Make menu.lst work with {py,pv}grub

Changes to the menu.lst to allow it to work with {py,pv}grub. Both
require the kernel command line as a string on the kernel line and
not as a separate cmdline file.

Change-Id: I658a84bb3a0a0eb5b0cdf823e55d45e67fd821d4
Merge changes I658a84bb,I1cad4891

* changes:
  Make menu.lst work with {py,pv}grub
  Add grub menu.lst to the ramdisk image