I ended up doing the following to get this to work:
In /opt/bitnami/apache2/conf/httpd.conf, change the following lines:
Comment out
DocumentRoot ‘/opt/bitnami/apache2/htdocs’
Add
DocumentRoot ‘/opt/bitnami/aps/moodle/htdocs’
Comment out
Directory ‘/opt/bitnami/apache2/htdocs’
Add
Directory ‘/opt/bitnami/apps/moodle/htdocs’
Seems to work for me.