mod_s2s_auth_dane: Fix traceback in DANE-TA check because unpack() moved It moved into the table package in Lua 5.2, error happens when compat is disabled or gone (ie 5.3+). This happened in DANE-TA, which is disabled by default.

This module blocks configured queries that change server state.

E.g. to make vCard storage read-only:

``` lua
readonly_stores = {
	vcard = { "vcard-temp", "vCard" };
}
```