Prevent Request.current_id test state leakage (#4808)

Author: Samze

spec/spec_helper.rb

@@ -179,6 +179,7 @@
       end
 
       VCAP::CloudController::SecurityContext.clear
+      VCAP::Request.current_id = nil
       allow_any_instance_of(VCAP::CloudController::UaaTokenDecoder).to receive(:uaa_issuer).and_return(UAAIssuer::ISSUER)
 
       mock_redis = MockRedis.new