net.box: finish worker fiber on Tarantool shutdown

Let's make sure net.box system fiber is finished on Tarantool shutdown as
we are going to free fibers stacks. If fiber is not finished it's stack
may have references to objects on heap. Thus as fiber stack will be freed
we will have FP memory leaks under ASAN.

Part of #9722

NO_CHANGELOG=internal
NO_DOC=internal

src/box/lua/net_box.c

@@ -3167,6 +3167,7 @@ luaT_netbox_transport_start(struct lua_State *L)
 		transport->self_ref = LUA_NOREF;
 		return luaT_error(L);
 	}
+	fiber_set_managed_shutdown(transport->worker);
 	transport->worker->f_arg = transport;
 	/*
 	 * Code that needs a temporary fiber-local Lua state may save some time

test/app-luatest/shutdown_test.lua

@@ -200,3 +200,31 @@ g_standby.test_shutdown_during_hot_standby = function(cg)
     end)
     test_no_hang_on_shutdown(cg.standby)
 end
+
+local g_netbox = t.group('netbox')
+
+g_netbox.before_each(function(cg)
+    cg.server = server:new()
+    cg.server:start()
+    cg.peer = server:new()
+    cg.peer:start()
+end)
+
+g_netbox.after_each(function(cg)
+    if cg.server ~= nil then
+        cg.server:drop()
+    end
+    if cg.peer ~= nil then
+        cg.peer:drop()
+    end
+end)
+
+-- Test shutdown with netbox connection.
+g_netbox.test_netbox_shutdown = function(cg)
+    cg.server:exec(function(uri)
+        local netbox = require('net.box')
+        local c = netbox.connect(uri)
+        rawset(_G, 'test_connection', c)
+    end, {cg.peer.net_box_uri})
+    test_no_hang_on_shutdown(cg.server)
+end