Fix a serious bug where the 'next' generation of the server would open
  a brand new mutex.  This patch creates a single mutex in the first config
  phase that survives for the life of the server (server->process->pool).

  Now one server generation to the next will respect the same mutex between
  one another, while the previous generation is still mopping up.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@99095 13f79535-47bb-0310-9956-ffa450edef68