Add infra_proxy_* classes in reclass storage

This will deploy proxy (Nginx) nodes for both OpenStack and StackLight
services.
diff --git a/salt/control/cluster/infra_proxy_cluster.yml b/salt/control/cluster/infra_proxy_cluster.yml
new file mode 100644
index 0000000..c82a947
--- /dev/null
+++ b/salt/control/cluster/infra_proxy_cluster.yml
@@ -0,0 +1,22 @@
+parameters:
+  salt:
+    control:
+      size:
+        infra.proxy:
+          cpu: 32
+          ram: 65536
+          disk_profile: small
+          net_profile: default
+      cluster:
+        internal:
+          domain: ${_param:cluster_domain}
+          engine: virt
+          node:
+            prx01:
+              provider: kvm01.${_param:cluster_domain}
+              image: ${_param:salt_control_trusty_image}
+              size: infra.proxy
+            prx02:
+              provider: kvm02.${_param:cluster_domain}
+              image: ${_param:salt_control_trusty_image}
+              size: infra.proxy