Clean up thread and process number defaults

for simple mpm.

- Before, simple wouldn't start without explicit
  config, because default numbers were 0
- log messages "more" and "less" were misleading


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@730873 13f79535-47bb-0310-9956-ffa450edef68