cleanup tmp key callbacks. each had assigned the same (1024 bit) value

in 3 different places.  the old code did nothing special in the case
of the export flag either.

add an ssl_log in each to trace when keys are being handed out.

add some XXX comments.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk/modules/ssl@93885 13f79535-47bb-0310-9956-ffa450edef68