Merge r1531679 from trunk:

mod_session: After parsing the value of the header specified by the
SessionHeader directive, remove the value from the response. PR 55279.

Submitted by: minfrin
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1536320 13f79535-47bb-0310-9956-ffa450edef68