skynet使用原生error，防止给替换 (#1906)

Co-authored-by: xingfan.yzj <xingfan.yzj@alibaba-inc.com>

lualib/skynet.lua

@@ -4,6 +4,7 @@ local skynet_require = require "skynet.require"
 local tostring = tostring
 local coroutine = coroutine
 local assert = assert
+local error = error
 local pairs = pairs
 local pcall = pcall
 local table = table