THRIFT-3246 Reduce the number of trivial warnings in Windows C++ CMake builds
Client: cpp
Patch: Ben Craig <bencraig@apache.org>

This closes #553
diff --git a/lib/cpp/test/concurrency/TimerManagerTests.h b/lib/cpp/test/concurrency/TimerManagerTests.h
index dda16ed..f4600fc 100644
--- a/lib/cpp/test/concurrency/TimerManagerTests.h
+++ b/lib/cpp/test/concurrency/TimerManagerTests.h
@@ -58,7 +58,7 @@
 
       delta = delta > _timeout ? delta - _timeout : _timeout - delta;
 
-      float error = delta / _timeout;
+      double error = double(delta) / _timeout;
 
       if (error < TEST_TOLERANCE) {
         _success = true;
@@ -119,7 +119,7 @@
           _monitor.wait(1000);
           assert(
               0 == "ERROR: This wait should time out. TimerManager dispatcher may have a problem.");
-        } catch (TimedOutException& ex) {
+        } catch (TimedOutException&) {
         }
 
         task.reset(new TimerManagerTests::Task(_monitor, timeout));