flow: clean up recycle queue at shutdown

Mostly for tests that don't start the recycler thread, make sure
all flows are cleaned up.

src/flow.c

@@ -444,10 +444,13 @@ void FlowShutdown(void)
 
     FlowPrintStats();
 
-    /* free spare queue */
+    /* free queues */
     while((f = FlowDequeue(&flow_spare_q))) {
         FlowFree(f);
     }
+    while((f = FlowDequeue(&flow_recycle_q))) {
+        FlowFree(f);
+    }
 
     /* clear and free the hash */
     if (flow_hash != NULL) {