app-emulation/nova-agent: Drop unused and outdated package

I'm not sure if we ever built it - it's not a dependency of anything
at all. Also one of its dependencies, dev-python/pyxenstore, was
dropped in 2014, so the package is broken for about seven years
now. Looks like that the rackspace oem package is rather pulling
nova-agent through the coreos-base/nova-agent-container package.

sdk_container/src/third_party/coreos-overlay/app-emulation/nova-agent/files/nova-agent.service

@@ -1,10 +0,0 @@
-[Unit]
-Description=Rackspace Nova Agent
-
-[Service]
-ExecStartPre=/bin/mount -t xenfs none /proc/xen
-ExecStart=/usr/sbin/nova-agent -n -o - -l info /usr/share/nova-agent/nova-agent.py
-ExecReload=/bin/kill -HUP $MAINPID
-
-[Install]
-WantedBy=network.target

sdk_container/src/third_party/coreos-overlay/app-emulation/nova-agent/metadata.xml

@@ -1,4 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
-<pkgmetadata>
-</pkgmetadata>

sdk_container/src/third_party/coreos-overlay/app-emulation/nova-agent/nova-agent-9999.ebuild

@@ -1,36 +0,0 @@
-#
-# Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
-# Distributed under the terms of the GNU General Public License v2
-# $Header:$
-#
-
-EAPI=2
-EGIT_REPO_URI="https://github.com/coreos/openstack-guest-agents-unix"
-inherit toolchain-funcs systemd git-2
-
-DESCRIPTION="Rackspace Nova Agent"
-HOMEPAGE="https://github.com/rackerlabs/openstack-guest-agents-unix"
-SRC_URI=""
-
-LICENSE="MIT"
-SLOT="0"
-KEYWORDS="~amd64 ~arm ~x86"
-IUSE=""
-
-DEPEND="dev-util/patchelf"
-RDEPEND="dev-python/pyxenstore"
-
-src_configure() {
-	./autogen.sh
-	econf
-}
-
-src_compile() {
-	emake
-}
-
-src_install() {
-	emake DESTDIR="${D}" install
-	systemd_dounit "${FILESDIR}"/${PN}.service
-	systemd_enable_service multi-user.target ${PN}.service
-}