Adds EPEL repo, cleans up rhel7 repos

This patch adds a new EPEL element for use with EL-based distros
in accordance with the official docs[1].  This patch also
modifies the rhel7 element to not use the hard-coded repo file.

[1] https://fedoraproject.org/wiki/EPEL

Change-Id: Ib2fa24b2d519837271a0e213a2dc5a012cc31f3c

elements/epel/README.md

@@ -0,0 +1,2 @@
+This element installs the Extra Packages for Enterprise Linux (EPEL)
+repository GPG key as well as configuration for yum.

elements/epel/pre-install.d/05-rpm-epel-release

@@ -0,0 +1,5 @@
+#!/bin/bash
+set -eu
+set -o pipefail
+
+yum install -y http://dl.fedoraproject.org/pub/epel/beta/7/x86_64/epel-release-7-1.noarch.rpm

elements/rhel7/pre-install.d/05-yum-repos

@@ -1,23 +0,0 @@
-#!/bin/bash
-
-set -eu
-set -o pipefail
-
-cat << EOF > /etc/yum.repos.d/epel.repo
-[epel]
-name=epel
-failovermethod=priority
-baseurl=http://download-i2.fedoraproject.org/pub/epel/beta/7/x86_64/
-enabled=1
-metadata_expire=7d
-gpgcheck=0
-EOF
-
-cat << EOF > /etc/yum.repos.d/bnemec-os-config.repo
-[bnemec-os-config]
-name=Copr repo for os-config owned by bnemec
-baseurl=http://copr-be.cloud.fedoraproject.org/results/bnemec/os-config/epel-7-x86_64/
-skip_if_unavailable=True
-gpgcheck=0
-enabled=1
-EOF