mod_http_oauth2: Fix removal of consumed authorization codes Fixes mod_http_oauth2.lua:34: bad argument #2 to 'difftime' (number expected, got nil) The extra preceding argument to :set stored the client-id#code as a value instead of clearing the key, and then later in the periodic cleanup timer this string would be indexed, producing a nil and a traceback

# 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