follow up to r930125

change log message when forcing worker into error state:
* APLOG_ERR instead of unsuppressible APLOG_NOTICE
* follow formatting of existing proxy messages more closely


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@962972 13f79535-47bb-0310-9956-ffa450edef68