mod_reqtimeout: follow up to r1853901: init stage name outside INIT_STAGE().

It helps both code readability where stages are initilized and potential
logging in the output filter (even if the stage is disabled).


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1853935 13f79535-47bb-0310-9956-ffa450edef68