output-tx: fix memleak

This fixes:

Direct leak of 31752 byte(s) in 3969 object(s) allocated from:
    #0 0x4c396b in malloc (/opt/suricata-asan/bin/suricata+0x4c396b)
    #1 0xe385b9 in OutputTxLogThreadInit /home/pmanev/sandnet-qa/stage/oisf/src/output-tx.c:193:34
    #2 0x106c255 in TmThreadsSlotPktAcqLoop /home/pmanev/sandnet-qa/stage/oisf/src/tm-threads.c:295:17
    #3 0x7fbc9fcb3181 in start_thread /build/eglibc-3GlaMS/eglibc-2.19/nptl/pthread_create.c:312

src/output-tx.c

@@ -260,6 +260,8 @@ static TmEcode OutputTxLogThreadDeinit(ThreadVars *tv, void *thread_data)
         store = next_store;
         logger = logger->next;
     }
+
+    SCFree(op_thread_data);
     return TM_ECODE_OK;
 }