Add virtual media boot support in ramdisk element.

This change adds support in ramdisk element for recognising
boot from virtual media cdrom and read the parameters from
the configuration file in virtual media floppy.
Change-Id: I28ca888b4ead4905f7141b38ed4b9a3614d00d26
Closes-Bug: #1321564
Merge "Add virtual media boot support in ramdisk element."