mod_proxy: Don't put non balancer-member workers in error state by

default for connection or 500/503 errors, and honor status=+I for
any error.  PR 48388.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1650028 13f79535-47bb-0310-9956-ffa450edef68