CLEANUP: task: remove unneeded tests before task_destroy()

Since previous commit it's not needed anymore to test a task pointer
before calling task_destory() so let's just remove these tests from
the various callers before they become confusing. The function's
arguments were also documented. The same should probably be done
with tasklet_free() which involves a test in roughly half of the
call places.

include/proto/task.h

@@ -329,6 +329,10 @@ static inline void __task_free(struct task *t)
 	_HA_ATOMIC_SUB(&nb_tasks, 1);
 }
 
+/* Destroys a task : it's unlinked from the wait queues and is freed if it's
+ * the current task or not queued otherwise it's marked to be freed by the
+ * scheduler. It does nothing if <t> is NULL.
+ */
 static inline void task_destroy(struct task *t)
 {
 	if (!t)

src/checks.c

@@ -3303,10 +3303,7 @@ int init_email_alert(struct mailers *mls, struct proxy *p, char **err)
 		struct email_alertq *q     = &queues[i];
 		struct check        *check = &q->check;
 
-		if (check->task) {
 		task_destroy(check->task);
-			check->task = NULL;
-		}
 		free_check(check);
 	}
 	free(queues);

src/flt_spoe.c

@@ -1275,9 +1275,7 @@ spoe_release_appctx(struct appctx *appctx)
 	}
 
 	/* Destroy the task attached to this applet */
-	if (spoe_appctx->task) {
 	task_destroy(spoe_appctx->task);
-	}
 
 	/* Notify all waiting streams */
 	list_for_each_entry_safe(ctx, back, &spoe_appctx->waiting_queue, list) {

src/haproxy.c

@@ -2290,9 +2290,7 @@ void deinit(void)
 		while (s) {
 			s_next = s->next;
 
-			if (s->check.task)
 			task_destroy(s->check.task);
-			if (s->agent.task)
 			task_destroy(s->agent.task);
 
 			if (s->check.wait_list.task)
@@ -2300,7 +2298,6 @@ void deinit(void)
 			if (s->agent.wait_list.task)
 				tasklet_free(s->agent.wait_list.task);
 
-			if (s->warmup)
 			task_destroy(s->warmup);
 
 			free(s->id);

src/mux_h1.c

@@ -431,7 +431,6 @@ static int h1_init(struct connection *conn, struct proxy *proxy, struct session
 	return 0;
 
   fail:
-	if (t)
 	task_destroy(t);
 	if (h1c->wait_event.task)
 		tasklet_free(h1c->wait_event.task);

src/mux_h2.c

@@ -575,7 +575,6 @@ static int h2_init(struct connection *conn, struct proxy *prx, struct session *s
   fail_stream:
 	hpack_dht_free(h2c->ddht);
   fail:
-	if (t)
 	task_destroy(t);
 	if (h2c->wait_event.task)
 		tasklet_free(h2c->wait_event.task);

src/session.c

@@ -448,11 +448,8 @@ static int conn_complete_session(struct connection *conn)
 		goto fail;
 
 	/* the embryonic session's task is not needed anymore */
-	if (sess->task) {
 	task_destroy(sess->task);
 	sess->task = NULL;
-	}
-
 	conn_set_owner(conn, sess, conn_session_free);
 
 	return 0;