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.