Merge r1703902 from trunk:

mod_proxy: Fix ProxySourceAddress binding failure with AH00938.  PR 56687.
Proposed by: Arne de Bruijn <apache arbruijn.dds.nl>
Reviewed by: ylavic

Submitted by: ylavic
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1706028 13f79535-47bb-0310-9956-ffa450edef68