Renaming users in JIRA creates new users in FishEye

When using JIRA for user management if a user is renamed in JIRA and then synchronized into FishEye this user appears to be only renamed in FishEye (the new username is listed), but looking at the DB shows that actually the previous user in FishEye is disabled, and a new one with the new username was created.

The user is then shown as deleted in reviews created by him.

Steps to Reproduce

1. Connect FishEye to JIRA for user management, configured as follows:
   
2. Rename a user in JIRA.
3. Run a Re-Sync in FishEye.
4. Notice the users seems to be renamed, but in DB a new user was created and the original user was disabled.