mod_slotmem_shm: follow up to r1831869.

Don't try to attach SHMs on startup, they might be from a previous crash and
prevent the server to start (on failure to reuse it).

On mpm_winnt though, the pre/post_config() phases are re-run in child process,
and the parent process already created the SMs, so they must be attached there.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1831870 13f79535-47bb-0310-9956-ffa450edef68