Unattended Jira upgrade fails

Issue Summary

Trying to upgrade Jira using the response.varfile as described here fails.

Steps to Reproduce

1. Download a Jira installer;
2. Upgrade Jira;
3. Use the created <installation-directory>/.install4j/response.varfile to make a second upgrade.

Expected Results

A successful upgrade.

Actual Results

We are presented with these messages in the terminal:

Unpacking JRE ...
Starting Installer ...
The installation directory has been set to /opt/atlassian2/jirasoftware.
It appears that JIRA is already installed in the directory you selected.  Please choose a different directory.

Workaround

In the response.varfile file, this line:

sys.confirmedUpdateInstallationString=False

Should actually look like this:

sys.confirmedUpdateInstallationString=true

Just make this replacement, and now the upgrade should happen successfully.