Change pidfile location in uwsgi_nailgun.yaml template

pid files should be placed in a standard directory.

In our case nailgun service (systemd) requires that file
to be placed in /var/run directory.

Blueprint: master-on-centos7

Compatible with CentOS6 master node

Change-Id: I97a2b6aac9f96628d41253bedc23b4667c60ac1d

deployment/puppet/nailgun/templates/uwsgi_nailgun.yaml.erb

@@ -12,7 +12,7 @@ uwsgi:
   module: nailgun.wsgi
   buffer-size: 49180
   listen: <%= @somaxconn %>
-  pidfile: /tmp/nailgun.pid
+  pidfile: /var/run/nailgun.pid
   logto: /var/log/nailgun/app.log
   mule: 1
   lazy: true