mod_proxy: Add ap_proxy_worker_get_name() and deprecate ap_proxy_worker_name().

mod_proxy: Add ap_proxy_worker_get_name() and deprecate ap_proxy_worker_name().

The latter requires a pool and returns a non constant string although it may
return worker shared data.

By computing the worker "UDS" name at init time we can return a constant name
in any case with no need for a pool, that's the new ap_proxy_worker_get_name().

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1912461 13f79535-47bb-0310-9956-ffa450edef68