Fail early if ramdisk type is dib, and not building
Fail early if ramdisk type is dib, and not building

Currently if IRONIC_BUILD_DEPLOY_RAMDISK is False, and ramdisk type is
DIB, we won't fail until the script attempts to run wget using an empty
address, this results in a hard to debug error. This patch ensures that
if we are not building the ramdisk but the ramdisk type is DIB that the
whole script fails early with an error message describing how to correct
the problem.

Change-Id: Ib9f31a3356ed64631129e5880e2657b0cf2014d2

openstack/ironic,pshchelo/ironic,NaohiroTamura/ironic,pshchelo/ironic,bacaldwell/ironic,SauloAislan/ironic,SauloAislan/ironic,NaohiroTamura/ironic,openstack/ironic,bacaldwell/ironic