MINOR: fd: move .exported into fdtab[].state

No need to keep this flag apart any more, let's merge it into the global
state.
diff --git a/src/sock_unix.c b/src/sock_unix.c
index 45631ac..9913f4f 100644
--- a/src/sock_unix.c
+++ b/src/sock_unix.c
@@ -289,7 +289,7 @@
 
 	/* for now, all regularly bound TCP listeners are exportable */
 	if (!(rx->flags & RX_F_INHERITED))
-		fdtab[fd].exported = 1;
+		HA_ATOMIC_OR(&fdtab[fd].state, FD_EXPORTED);
 
 	return err;