MEDIUM: cli: worker socketpair is unstoppable

In master-worker mode, the socketpair CLI listener of the worker is now
marked unstoppable, which allows to connect to the CLI of an old process
which is in a leaving state, allowing to debug it.
diff --git a/src/cli.c b/src/cli.c
index 85e344d..720a9b4 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -2336,7 +2336,7 @@
 		l->backlog = global.stats_fe->backlog;
 		l->accept = session_accept_fd;
 		l->default_target = global.stats_fe->default_target;
-		l->options |= LI_O_UNLIMITED;
+		l->options |= (LI_O_UNLIMITED | LI_O_NOSTOP);
 		/* it's a sockpair but we don't want to keep the fd in the master */
 		l->options &= ~LI_O_INHERITED;
 		l->nice = -64;  /* we want to boost priority for local stats */