Always install latest EPEL

Having issues with the centos7 job, that seem to be because they use
an old snapshot that hasn't updated to the latest EPEL.  Thus we
re-install it to ensure we're getting the latest.

Change-Id: I7930f3e05ee953dab80b06142c17d6aa70f2c2d1

stack.sh

@@ -234,8 +234,14 @@ fi
 
 if [[ is_fedora && ( $DISTRO == "rhel6" || $DISTRO == "rhel7" ) ]]; then
     # RHEL requires EPEL for many Open Stack dependencies
-    if ! sudo yum repolist enabled epel | grep -q 'epel'; then
-        echo "EPEL not detected; installing"
+
+    # note we always remove and install latest -- some environments
+    # use snapshot images, and if EPEL version updates they break
+    # unless we update them to latest version.
+    if sudo yum repolist enabled epel | grep -q 'epel'; then
+        uninstall_package epel-release || true
+    fi
+
     # This trick installs the latest epel-release from a bootstrap
     # repo, then removes itself (as epel-release installed the
     # "real" repo).
@@ -251,7 +257,7 @@ if [[ is_fedora && ( $DISTRO == "rhel6" || $DISTRO == "rhel7" ) ]]; then
     fi
 
     cat <<EOF | sudo tee /etc/yum.repos.d/epel-bootstrap.repo
-[epel]
+[epel-bootstrap]
 name=Bootstrap EPEL
 mirrorlist=http://mirrors.fedoraproject.org/mirrorlist?repo=epel-$epel_ver&arch=\$basearch
 failovermethod=priority
@@ -259,11 +265,10 @@ enabled=0
 gpgcheck=0
 EOF
     # bare yum call due to --enablerepo
-        sudo yum --enablerepo=epel -y install epel-release || \
+    sudo yum --enablerepo=epel-bootstrap -y install epel-release || \
         die $LINENO "Error installing EPEL repo, cannot continue"
     # epel rpm has installed it's version
     sudo rm -f /etc/yum.repos.d/epel-bootstrap.repo
-    fi
 
     # ... and also optional to be enabled
     is_package_installed yum-utils || install_package yum-utils