Use ffi bindings instead of box.info for uptime/version.

src/lua/init.lua

@@ -6,6 +6,10 @@ local ffi = require('ffi')
 ffi.cdef[[
 char *
 tarantool_error_message(void);
+const char *
+tarantool_version(void);
+double
+tarantool_uptime(void);
 ]]
 
 local pcall_lua = pcall
@@ -31,6 +35,6 @@ end
 -- This function automatically called by the server for
 -- any new admin client.
 function motd()
-	return "Tarantool " .. box.info.version,
-		   "Uptime: " .. box.info.uptime
+	return "Tarantool " .. ffi.string(ffi.C.tarantool_version()),
+		   "Uptime: " .. math.floor(ffi.C.tarantool_uptime())
 end