Fix CTF backend trace event recursion problem

Any tracing library should be independent of the code it is tracing. This is not the case with CTF backend, it is build together with the same codes it is trying to trace. It uses threds, mutexes and other classes, which might potentially have traces in them in the future(not currently). This means that the tracing backend itself can generate new trace events creating infinite recursive loop. This doesn't just consern only the plugin, but any code inside Q_TRACE_XXX macros.