fix: use old-style portable IOstream redirection syntax for appending to logfile

templates/opt/tivoli/tsm/client/ba/bin/dsm.sys.j2

@@ -23,7 +23,10 @@ Servername {{ servername }}
    passwordaccess     {{ passwordaccess }}
    managedservices    {{ managedservices }}
 
-   PRESCHEDULECMD     '/opt/backup_archivematica_repos/bin/backup_am_github_repos_and_issues.sh'
+*  The PreScheduleCmd doesn't use the bash to call commands, so it is not
+*  possible to use Bash 4+ syntax for IOstream redirection. Use the classic
+*  "2>&1" style instead!
+   PRESCHEDULECMD     '/opt/backup_archivematica_repos/bin/backup_am_github_repos_and_issues.sh --backup-dir /opt/backup_archivematica_repos/ >> /var/log/ambackup.log 2>&1'
 
    Domain             {{ domain }}