Use alternate way to specify and load the root fs

The way that upstream has chosen doesn't work with the HP
servers, even though it works fine an the master desktop
nodes and the development cluster.

See https://docs.fedoraproject.org/en-US/fedora-coreos/live-booting-ipxe/#_pxe_images
and coreos/fedora-coreos-tracker#390.

bare-metal/fedora-coreos/kubernetes/profiles.tf

@@ -1,28 +1,26 @@
 locals {
   remote_kernel = "https://builds.coreos.fedoraproject.org/prod/streams/${var.os_stream}/builds/${var.os_version}/x86_64/fedora-coreos-${var.os_version}-live-kernel-x86_64"
-  remote_initrd = [
-    "https://builds.coreos.fedoraproject.org/prod/streams/${var.os_stream}/builds/${var.os_version}/x86_64/fedora-coreos-${var.os_version}-live-initramfs.x86_64.img",
-    "https://builds.coreos.fedoraproject.org/prod/streams/${var.os_stream}/builds/${var.os_version}/x86_64/fedora-coreos-${var.os_version}-live-rootfs.x86_64.img"
-  ]
+  remote_initrd = ["https://builds.coreos.fedoraproject.org/prod/streams/${var.os_stream}/builds/${var.os_version}/x86_64/fedora-coreos-${var.os_version}-live-initramfs.x86_64.img"]
 
   remote_args = [
     "ip=dhcp",
     "rd.neednet=1",
+    "initrd=fedora-coreos-${var.os_version}-live-initramfs.x86_64.img",
+    "coreos.live.rootfs_url=https://builds.coreos.fedoraproject.org/prod/streams/${var.os_stream}/builds/${var.os_version}/x86_64/fedora-coreos-${var.os_version}-live-rootfs.x86_64.img",
     "coreos.inst.ignition_url=${var.matchbox_http_endpoint}/ignition?uuid=$${uuid}&mac=$${mac:hexhyp}",
     "coreos.inst.image_url=https://builds.coreos.fedoraproject.org/prod/streams/${var.os_stream}/builds/${var.os_version}/x86_64/fedora-coreos-${var.os_version}-metal.x86_64.raw.xz",
     "console=tty0",
     "console=ttyS0",
   ]
 
   cached_kernel = "/assets/fedora-coreos/fedora-coreos-${var.os_version}-live-kernel-x86_64"
-  cached_initrd = [
-    "/assets/fedora-coreos/fedora-coreos-${var.os_version}-live-initramfs.x86_64.img",
-    "/assets/fedora-coreos/fedora-coreos-${var.os_version}-live-rootfs.x86_64.img"
-  ]
+  cached_initrd = ["/assets/fedora-coreos/fedora-coreos-${var.os_version}-live-initramfs.x86_64.img"]
 
   cached_args = [
     "ip=dhcp",
     "rd.neednet=1",
+    "initrd=fedora-coreos-${var.os_version}-live-initramfs.x86_64.img",
+    "coreos.live.rootfs_url=${var.matchbox_http_endpoint}/assets/fedora-coreos/fedora-coreos-${var.os_version}-live-rootfs.x86_64.img",
     "coreos.inst.ignition_url=${var.matchbox_http_endpoint}/ignition?uuid=$${uuid}&mac=$${mac:hexhyp}",
     "coreos.inst.image_url=${var.matchbox_http_endpoint}/assets/fedora-coreos/fedora-coreos-${var.os_version}-metal.x86_64.raw.xz",
     "console=tty0",