Make tests less verbose

The numeric values of the labels aren't of value when inspecting test
results. For this reason, it makes sense to put them behind the verbose
flag to make test framework debugging happen purpose.

maxscale-system-test/testconnections.h

@@ -186,7 +186,7 @@ public:
     /**
      * @brief verbose if true more printing activated
      */
-    bool verbose;
+    static bool verbose;
 
     /**
      * @brief smoke if true all tests are executed in quick mode