output-file: fix memleak

output-file: fix memleak

This fixes:

Direct leak of 31856 byte(s) in 3982 object(s) allocated from:
    #0 0x4c396b in malloc (/opt/suricata-asan/bin/suricata+0x4c396b)
    #1 0xd7ff39 in OutputFileLogThreadInit /home/pmanev/sandnet-qa/stage/oisf/src/output-file.c:182:34
    #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