Add a call to apr_hook_deregister_all() in the clear_module_list function.

Add a call to apr_hook_deregister_all() in the clear_module_list function.
The basic problem was that when we load the modules, we call the
register_hooks() function from the module, but then we clear the module
list for all active modules, and add them back in one at a time.  When we
add them back, we re-call the register_hooks() function, thus adding
each function a second time.  This was causing apache.org to log every
request twice in the access log.  By calling apr_hook_deregister_all()
when we unload the module, the second call to register the hooks is the
only call that matters.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@87774 13f79535-47bb-0310-9956-ffa450edef68