AthenaKernel: Prevent implicit StatusCode conversion in CHECK

Prevent the following code from compiling as that relies on an
implicit conversion of the return value of `myFunc` into a `StatusCode`:
```
int myFunc();

CHECK(myFunc());
```

Control/AthenaKernel/AthenaKernel/errorcheck.h

 // This file's extension implies that it's C, but it's really -*- C++ -*-.
 
 /*
-  Copyright (C) 2002-2019 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 */
 
 /**
@@ -396,13 +396,13 @@ private:
     BOOST_PP_OVERLOAD(CHECK_WITH_CONTEXT_, __VA_ARGS__)(__VA_ARGS__)
 
 #define CHECK_WITH_CONTEXT_2(EXP, CONTEXT_NAME) do {       \
-    StatusCode sc__(EXP);                                  \
+    StatusCode sc__ = (EXP);                               \
     if (! sc__.isSuccess())                                \
       CHECK_FAILED(EXP, CONTEXT_NAME, sc__, sc__);         \
   } while (0)
 
 #define CHECK_WITH_CONTEXT_3(EXP, CONTEXT_NAME, RET) do {  \
-    StatusCode sc__(EXP);                                  \
+    StatusCode sc__ = (EXP);                               \
     if (! sc__.isSuccess())                                \
       CHECK_FAILED(EXP, CONTEXT_NAME, sc__, RET);          \
   } while (0)