Comment 15 for bug 1495988

Request for SRU sponsoring

[Impact]
 * hang until ProxyTimeout timeout if ProxyErrorOverride is set
 * see https://bz.apache.org/bugzilla/show_bug.cgi?id=53420 for more

[Test Case]
 * use the feature of https://httpd.apache.org/docs/current/mod/mod_proxy.html#proxyerroroverride

[Regression Potential]
 * the patch is small and already backported by Apache people which is good
 * The changes are local to mod_proxy only which should limit the potential fallout
 * all basic tests I did still work, but we have to rely on a real test by the reporter from proposed for the actual Test