[tests] Fix threading issue with parallel testing with non-threadsafe rspec mocks

Author: chadlwilson

src/spec/ruby/rack/application_spec.rb

@@ -792,8 +792,9 @@ def createRackServletWrapper(runtime, rackup, filename)
     expect(millis).to be >= 90 # waited about ~ 0.10 secs
   end
 
-  it "initializes initial runtimes in paralel (with wait set to false)" do
-    allow(@factory).to receive(:init)
+  it "initializes initial runtimes in parallel (with wait set to false)" do
+    @factory = double("factory (non-tracking)", null_object: true)
+    allow(@factory).to receive(:init).with(any_args)
     allow(@factory).to receive(:newApplication) do
       app = double "app"
       allow(app).to receive(:init) do