Ruby - Adding warning instead of Validation failure when unknown prop…

…erty found on object. (Azure#1263)

src/client/Ruby/ms-rest/lib/ms_rest/serialization.rb

@@ -318,7 +318,7 @@ def serialize_composite_type(mapper, object, object_name)
             begin
               instance_variable = object.instance_variable_get("@#{key}")
             rescue NameError
-              fail ValidationError, "instance variable '#{key}' is expected on '#{object.class}'."
+              warn("Instance variable '#{key}' is expected on '#{object.class}'.")
             end
 
             if !instance_variable.nil? && instance_variable.respond_to?(:validate)