setting up AJP secret between Apache and Tomcat
mod_proxy_ajp
didn't support the secret
option before Apache 2.5.
Please refer:
v2.4 document: https://httpd.apache.org/docs/2.4/mod/mod_proxy_ajp.html
v2.5 document: https://httpd.apache.org/docs/trunk/mod/mod_proxy_ajp.html