BUG/MINOR: task: fix thread assignment in tasklet_kill()

tasklet_kill() was introduced in 2.5-dev4 with commit 7b368339a
("MEDIUM: task: implement tasklet kill"), but a comparison error
there makes tasklets killed on thread 1 assigned to the killing
thread. Fortunately, the function was finally not used so there's
no harm right now, hence the minor tag, but this must be fixed and
backported in case a later fix relies on it.

This should be backported to 2.5.

src/task.c

@@ -126,7 +126,7 @@ void tasklet_kill(struct tasklet *t)
 		 * as soon as possible.
 		 */
 		if (_HA_ATOMIC_CAS(&t->state, &state, state | TASK_IN_LIST | TASK_KILLED)) {
-			thr = t->tid > 0 ? t->tid: tid;
+			thr = t->tid >= 0 ? t->tid : tid;
 			MT_LIST_APPEND(&ha_thread_ctx[thr].shared_tasklet_list,
 			               list_to_mt_list(&t->list));
 			_HA_ATOMIC_INC(&ha_thread_ctx[thr].rq_total);