Further review of ApplicationFilterConfig.
Inline the setFilterDef() method.
In the constructor the filterDef is never null and there is no need to care about destroying a filter. Thus the code is simplier.
The method was package-visible, thus there should not be any 3rd party callers.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1429167 13f79535-47bb-0310-9956-ffa450edef68