mod_s2s_keepalive: Use timestamp as iq @id RFC 6120 implies that the id attribute must be unique within a stream. This should fix problems with remote servers that enforce uniqueness and don't answer duplicated ids. If it doesn't do that, then at least you can get a guesstimate at round-trip time from the difference between the result iq stanza and the timestamp it was logged without having to go look for when it was sent, or needing to keep state.

# 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