Update the map file for ng to use nginx as the redhat user instead of httpd.

nginx/ng/map.jinja

@@ -18,7 +18,7 @@
         'RedHat': {
             'package': 'nginx',
             'service': 'nginx',
-            'webuser': 'httpd',
+            'webuser': 'nginx',
             'conf_file': '/etc/nginx/nginx.conf',
             'vhost_available': '/etc/nginx/conf.d',
             'vhost_enabled': '/etc/nginx/conf.d',