MEDIUM: threads/fd: Initialize the process mask during the call to fd_insert

Listeners will allow any threads to process the corresponding fd. But for other
FDs, we limit the processing to the current thread.
diff --git a/src/haproxy.c b/src/haproxy.c
index 7f48514..170b002 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -2228,7 +2228,7 @@
 	fcntl(mworker_pipe[0], F_SETFL, O_NONBLOCK);
 	fdtab[mworker_pipe[0]].owner = mworker_pipe;
 	fdtab[mworker_pipe[0]].iocb = mworker_pipe_handler;
-	fd_insert(mworker_pipe[0]);
+	fd_insert(mworker_pipe[0], MAX_THREADS_MASK);
 	fd_want_recv(mworker_pipe[0]);
 }