MEDIUM: mworker: set the iocb of the socketpair without using fd_insert()

The worker was previously changing the iocb of the socketpair in the
worker by mworker_accept_wrapper(). However, it was done using
fd_insert() instead of changing directly the callback in the
fdtab[].iocb pointer.

This patch cleans up this by part by removing fd_insert().

It also stops setting tid_bit on the thread mask, the socketpair will be
handled by any thread from now.

(cherry picked from commit 34aae2fd1293872345056a32dec8047a67c3d852)
[wla: Must be backported where 36d9097c ("MINOR: fd: Add BUG_ON checks
on fd_insert()") is backported]
Signed-off-by: William Lallemand <wlallemand@haproxy.org>
(cherry picked from commit 20c88db68710780e766cfc8b55b0e12b8ad651f8)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 79324f9679cd584f76c83e5a82c28f1dacb023cf)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/src/mworker.c b/src/mworker.c
index 7a8feda..d4ba7d8 100644
--- a/src/mworker.c
+++ b/src/mworker.c
@@ -398,7 +398,7 @@
 	/* In multi-tread, we need only one thread to process
 	 * events on the pipe with master
 	 */
-	fd_insert(proc_self->ipc_fd[1], fdtab[proc_self->ipc_fd[1]].owner, mworker_accept_wrapper, tid_bit);
+	fdtab[proc_self->ipc_fd[1]].iocb = mworker_accept_wrapper;
 	fd_want_recv(proc_self->ipc_fd[1]);
 	return 1;
 }