Issue hook fires with incorrect user when using Mercurial

As seen on: https://support.atlassian.com/browse/BBS-22804

Seems that when somebody pulls code, commits and pushes using the 'Issues' hook with Mercurial, there is a case where the issue is updated with the wrong person:

https://bitbucket.org/gluent/offload/issues/25/implement-option-to-preserve-load-table\\
https://bitbucket.org/gluent/offload/commits/ca69d182c939

In this scenario, Martin Nash committed and pushed the changes, while the issue is labeled as being closed by Paul Bridger.