Fix the typo (probably). The %~na is something windows

help for batch files does not recognize.
Anyhow, renaming to the %~nf there is no more
%~na.default file generated inside conf/extra on install.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@424688 13f79535-47bb-0310-9956-ffa450edef68