Disable tracing of span starts by default

Signed-off-by: Gavin Halliday <[email protected]>

system/jlib/jtrace.cpp

@@ -743,7 +743,7 @@ class CTraceManager : implements ITraceManager, public CInterface
 private:
     bool enabled = true;
     bool optAlwaysCreateGlobalIds = false;
-    bool optLogSpanStart = true; // Likely to change to false at a later date
+    bool optLogSpanStart = false;
     bool optLogSpanFinish = true;
     StringAttr moduleName;