mod_smacks: Fix duplicate sleep behavior when replacing a session
Fixes that an extra watchdog was set, leaking the previous one, which
went on to do behave as if the session times out.
For full information on our dependencies, version requirements, and
where to find them, see https://prosody.im/doc/depends
If you have luarocks available on your platform, install the following:
- luaexpat
- luasocket
- luafilesystem
- luasec