Run yum repolist commands as root

Otherwise you get yum errors like [1] when you run stack.sh as !root.
The solution is to run yum commands as root so it can access the right
certs

[1] https://access.redhat.com/site/solutions/312413

Change-Id: I54b0df13508c50aba67e23da11953c536933917a
diff --git a/stack.sh b/stack.sh
index 9cdf264..b3c507b 100755
--- a/stack.sh
+++ b/stack.sh
@@ -181,7 +181,7 @@
     # Installing Open vSwitch on RHEL6 requires enabling the RDO repo.
     RHEL6_RDO_REPO_RPM=${RHEL6_RDO_REPO_RPM:-"http://rdo.fedorapeople.org/openstack-havana/rdo-release-havana.rpm"}
     RHEL6_RDO_REPO_ID=${RHEL6_RDO_REPO_ID:-"openstack-havana"}
-    if ! yum repolist enabled $RHEL6_RDO_REPO_ID | grep -q $RHEL6_RDO_REPO_ID; then
+    if ! sudo yum repolist enabled $RHEL6_RDO_REPO_ID | grep -q $RHEL6_RDO_REPO_ID; then
         echo "RDO repo not detected; installing"
         yum_install $RHEL6_RDO_REPO_RPM || \
             die $LINENO "Error installing RDO repo, cannot continue"
@@ -189,7 +189,7 @@
 
     # RHEL6 requires EPEL for many Open Stack dependencies
     RHEL6_EPEL_RPM=${RHEL6_EPEL_RPM:-"http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm"}
-    if ! yum repolist enabled epel | grep -q 'epel'; then
+    if ! sudo yum repolist enabled epel | grep -q 'epel'; then
         echo "EPEL not detected; installing"
         yum_install ${RHEL6_EPEL_RPM} || \
             die $LINENO "Error installing EPEL repo, cannot continue"