qc_thread_init() must now explicitly be called in every thread
and not just in other threads but the one where qc_process_init()
is called.
This change was caused by QC_INIT_SELF initialization actually
being performed in query_classifier.cc. Before this change, there
actually was a leak in the routing worker running in the main
thread, the query classification cache was created twice.
5c1a1c2700