AJP_EBAD_METHOD is also a bad request so return HTTP_NOT_IMPLEMENTED

Submitted by: jfclere
Backports: r1166551, r1166657
Reviewed by: wrowe, jorton

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1167158 13f79535-47bb-0310-9956-ffa450edef68