mod_proxy: Fixup UDS filename for mod_proxy called through r->handler.

mod_proxy: Fixup UDS filename for mod_proxy called through r->handler.

* modules/proxy/proxy_util.c:
  Export ap_proxy_fixup_uds_filename() from fix_uds_filename.
  Call it from ap_proxy_pre_request() even for rewritten balancer workers.

* modules/proxy/mod_proxy.h:
  Declare ap_proxy_fixup_uds_filename()

* modules/proxy/mod_proxy.c:
  Fixup UDS filename from r->handler in proxy_handler().

* include/ap_mmn.h:
  Bump MMN minor for ap_proxy_fixup_uds_filename()

mod_proxy: follow up to r1918626: Simplify ap_proxy_fixup_uds_filename() and callers.

Merges r1918626, r1918647 from trunk
GH: closes #457

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1918666 13f79535-47bb-0310-9956-ffa450edef68