correctly free thread_data options at the topmost parent process

for non-threaded mode: since thread_data::eo is a pointer within shared 
memory between the topmost fio parent process and its children let the 
fio parent process set the pointer to NULL as just it frees its copy of 
'eo' as memory previously allocated by means of 'malloc' meaning that 
each child and the parent process itself must free it

for threaded mode we leave it as it has always been

also we do not need to check td->io_ops for being able to free td->io in
 fio_options_free()

Signed-off-by: Denis Pronin <dannftk@yandex.ru>

backend.c

@@ -2494,10 +2494,7 @@ static void run_threads(struct sk_out *sk_out)
  strerror(ret));
  } else {
  pid_t pid;
- void *eo;
  dprint(FD_PROCESS, "will fork\n");
- eo = td->eo;
- read_barrier();
  pid = fork();
  if (!pid) {
  int ret;
@@ -2506,7 +2503,6 @@ static void run_threads(struct sk_out *sk_out)
  _exit(ret);
  } else if (__td_index == fio_debug_jobno)
  *fio_debug_jobp = pid;
- free(eo);
  free(fd);
  fd = NULL;
  }

ioengines.c

@@ -238,7 +238,8 @@ void free_ioengine(struct thread_data *td)
  if (td->eo && td->io_ops->options) {
  options_free(td->io_ops->options, td->eo);
  free(td->eo);
- td->eo = NULL;
+ if (td->o.use_thread)
+ td->eo = NULL;
  }
 
  if (td->io_ops->dlhandle) {

options.c

@@ -5829,9 +5829,9 @@ void fio_options_free(struct thread_data *td)
  options_free(fio_options, &td->o);
  if (td->eo && td->io_ops && td->io_ops->options) {
  options_free(td->io_ops->options, td->eo);
- free(td->eo);
- td->eo = NULL;
  }
+ free(td->eo);
+ td->eo = NULL;
 }
 
 void fio_dump_options_free(struct thread_data *td)