fw: use UnitTestTimeFixture in NCC test case

This commit also changes StrategyTester<S>::onAction to use Signal.

refs #2163

Change-Id: Icd30cfa640972c53efdd8c7f7164b7eb9fc34c1e
diff --git a/tests/test-common.hpp b/tests/test-common.hpp
index e3bc0b5..247337d 100644
--- a/tests/test-common.hpp
+++ b/tests/test-common.hpp
@@ -127,6 +127,8 @@
     }
   }
 
+  friend class LimitedIo;
+
 protected:
   shared_ptr<time::UnitTestSteadyClock> steadyClock;
   shared_ptr<time::UnitTestSystemClock> systemClock;