Configure JIRA incoming mail (IMAP) to use STARTTLS

By default JAVA does not use STARTTLS. To fix this we have to adjust the following file:
/opt/atlassian/jira/bin/setenv.sh

Change:
JVM_REQUIRED_ARGS='-Djava.awt.headless=true...

To:
JVM_REQUIRED_ARGS='-Dmail.imap.starttls.enable=true -Djava.awt.headless=true...