mod_s2s_keepalive: Ignore errors from the local server If a stanza can't be delivered and instead an bounce is generated, the origin of the error, when different from the stanza 'from' should be indicated in the 'by' attribute of the <error>, which we look for here so this doesn't count as a successful ping. An error that does come from the remote means we have connectivity, but probably no XEP-0199 handling. This is fine. We care about connectivity, not protocol.

# Introduction

This module sends a [version query][xep0092] to clients when they
connect, and logs the response, allowing statistics of client usage to
be recorded.

Note that since this is per connection, there will be a bias towards
mobile clients on bad connections.

## Example

    info    Running Running Swift version 4.0