mod_proxy_http: don't strip EOS when spooling request body to file.

mod_proxy_http: don't strip EOS when spooling request body to file.

To prevent stream_reqbody() from sending the FILE and EOS bucket in separate
brigades, and thus apr_file_setaside() to trigger if network congestion occurs
with the backend, restore the EOS in spool_reqbody_cl() which was stripped
when spooling the request body to a file.

Until APR r1878279 is released (and installed by users), apr_file_setaside()
on a temporary file (mktemp) will simply drop the file cleanup, leaking the
fd and inode..

This fixes BZ 64452.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1878280 13f79535-47bb-0310-9956-ffa450edef68