mod_s2s_keepalive: Fix identification of replies (error-replies included) Typo? This condition is supposed to filter out get and set (and anything else), not errors, which can still mean that there's connectivity, just no handling of XEP-0199.

This module blocks configured queries that change server state.

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

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