Confluence will not start if the installation files are moved because the Linux Installer hardcodes JRE_HOME in setenv.sh.

Steps to reproduce

1. Install Linux using the installer
2. Specify a particular installation folder
3. Once the installer is finished, move the files to another folder
   • Observe that Confluence will not start, and this error appears in the catalina logs (where /opt/ was the original install location):

     /opt/atlassian-confluence-5.2.3/bin/catalina.sh: line 375: /opt/jre//bin/java: No such file or directory
     

4. Edit setenv.sh and edit JRE_HOME to point to the JRE folder in the new location
   • Observe that Confluence will now start

This should be a relative location based on the location of the script, not hardcoded.