Adding list_zones call to OpenStack

lib/fog/openstack/compute.rb

@@ -189,6 +189,9 @@ module Fog
       request :list_hosts
       request :get_host_details
 
+      # Zones
+      request :list_zones
+
       class Mock
         attr_reader :auth_token
         attr_reader :auth_token_expiration

lib/fog/openstack/requests/compute/list_zones.rb

@@ -0,0 +1,32 @@
+module Fog
+  module Compute
+    class OpenStack
+      class Real
+        def list_zones(*args)
+          request(
+            :expects  => 200,
+            :method   => 'GET',
+            :path     => 'os-availability-zone.json'
+          )
+        end
+      end
+
+      class Mock
+        def list_zones(*args)
+          Excon::Response.new(
+            :body   => { "availabilityZoneInfo" => [
+                  {
+                      "zoneState" => {
+                          "available" => true
+                      },
+                      "hosts" => nil,
+                      "zoneName" => "nova"
+                  }
+              ] },
+            :status => 200
+          )
+        end
+      end
+    end
+  end
+end