.conf suffix for the horizon config on Fedora

On Fedora by default the *.conf imported only from
the /etc/httpd/conf.d/.

Changing the default config name to horizon.conf with all
distribution in order to have a simple logic.

Change-Id: I08c3e825f697640fd73ac1f9c569f313abc3c04f
diff --git a/lib/horizon b/lib/horizon
index 89bd659..a879d1e 100644
--- a/lib/horizon
+++ b/lib/horizon
@@ -106,13 +106,13 @@
     sudo mkdir -p $HORIZON_DIR/.blackhole
 
     HORIZON_REQUIRE=''
-    local horizon_conf=/etc/$APACHE_NAME/$APACHE_CONF_DIR/horizon
+    local horizon_conf=/etc/$APACHE_NAME/$APACHE_CONF_DIR/horizon.conf
     if is_ubuntu; then
         # Clean up the old config name
         sudo rm -f /etc/apache2/sites-enabled/000-default
         # Be a good citizen and use the distro tools here
         sudo touch $horizon_conf
-        sudo a2ensite horizon
+        sudo a2ensite horizon.conf
         # WSGI isn't enabled by default, enable it
         sudo a2enmod wsgi
     elif is_fedora; then