mod_proxy: Detect unix: scheme syntax errors at load time.

* modules/proxy/mod_proxy.c(add_pass, add_member, set_proxy_param,
                            proxysection):
  Check return value of ap_proxy_de_socketfy().

* modules/proxy/proxy_util.c(ap_proxy_get_worker_ex):
  Check return value of ap_proxy_de_socketfy().



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1895914 13f79535-47bb-0310-9956-ffa450edef68
