MINOR: connection: use MT_LIST_ADDQ() to add connections to idle lists

When a connection is added to an idle list, it's already detached and
cannot be seen by two threads at once, so there's no point using
TRY_ADDQ, there will never be any conflict. Let's just use the cheaper
ADDQ.
diff --git a/src/ssl_sock.c b/src/ssl_sock.c
index 54da3a0..69f6835 100644
--- a/src/ssl_sock.c
+++ b/src/ssl_sock.c
@@ -5676,9 +5676,9 @@
 		struct server *srv = objt_server(conn->target);
 
 		if (conn_in_list == CO_FL_SAFE_LIST)
-			MT_LIST_TRY_ADDQ(&srv->safe_conns[tid], &conn->list);
+			MT_LIST_ADDQ(&srv->safe_conns[tid], &conn->list);
 		else
-			MT_LIST_TRY_ADDQ(&srv->idle_conns[tid], &conn->list);
+			MT_LIST_ADDQ(&srv->idle_conns[tid], &conn->list);
 	}
 	return NULL;
 }