Use readlink to get script path

So we can support usage:
ln -s ~/source/.../disk-image-create ~/bin/

Change-Id: Id54b613a247679b98cef3e9a6f37cd93155d029e
Add dhcp support for ramdisk element.

This change adds support for retrieving the IP
through DHCP if 'ip' was not provided as a kernel
command-line argument by pxelinux.  This is used
when the kernel/ramdisk is booted by virtual media.

Change-Id: I1097ce5b56ad40f2d6dc3181681d54f924ec7145
Closes-Bug: #1321563
Merge "Use readlink to get script path"
Merge "Add dhcp support for ramdisk element."