For example, a cloud may get better preformance from a cinder volume
then the local compute drive. As a result, give nodepool to option to
choose if the server should boot from volume or not.
Change-Id: I3faefe99096fef1fe28816ac0a4b28c05ff7f0ec
Depends-On: If58cd96b0b9ce4569120d60fbceb2c23b2f7641d
Signed-off-by: Paul Belanger <pabelanger@redhat.com>