Since we are using bash syntax in some of the element fragments,
we should make sure we use bash for all of them, so that things don't
break on systems where /bin/sh != /bin/bash.
Change-Id: If2f043c57aa4e1492b7f9839213ef6123f683612
Changing the grub config makes no sense in a build not heading for a vm
and may fail because grub is removed from images not including the vm
element. Forcing textmode for those images would be better done in nova.
Change-Id: I1c5b89e551e62df2463200b1889cb2342498c7dd