tests: print MM logs only on verbose test mode

Therefore, avoid needing ENABLE_TEST_MESSAGE_TRACES build symbol.

plugins/cinterion/tests/test-modem-helpers-cinterion.c

@@ -865,17 +865,17 @@ _mm_log (const char *loc,
          const char *fmt,
          ...)
 {
-#if defined ENABLE_TEST_MESSAGE_TRACES
-    /* Dummy log function */
     va_list args;
     gchar *msg;
 
+    if (!g_test_verbose ())
+        return;
+
     va_start (args, fmt);
     msg = g_strdup_vprintf (fmt, args);
     va_end (args);
     g_print ("%s\n", msg);
     g_free (msg);
-#endif
 }
 
 int main (int argc, char **argv)