405 for POST request after overriding DefaultServlet

Issue

• We've mapped a custom servlet to /, overriding the DefaultServlet. We then mapped the DefaultServlet back to .html:

  <servlet-mapping>
    <servlet-name>default</servlet-name>
    <url-pattern>*.html</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
     <servlet-name>CustomServlet</servlet-name>
     <url-pattern>/</url-pattern>  
  </servlet-mapping> 

• And now we see a 405 when attempting a POST request against that CustomServlet when not specifying a file name (for example, /app/). This worked previously on EAP 6 and JBossWeb