Clean up config.yaml.erb

[yl3w]

Config currently specified the following properties

:ipxe:
    :images:
        :initrd: <%= @ipxe_initrd %>
        :kernel: <%= @ipxe_kernel %>
    :kernel_flags: <%= @ipxe_kernel_flags %>
    :menu_default: intake
    :image_server: http://<%= @image_service %>/genesis
:genesis_server: http://<%= @genesis_service %>

I don't believe these are used by genesis itself. Speaking with @roymarantz, I understand these were moved to configs in PHIL. Please verify and get rid of these