Don't stop sending a request if EAGAIN is returned, which will only

Don't stop sending a request if EAGAIN is returned, which will only
happen if both the write and subsequent wait are returning EAGAIN,
and count posted bytes correctly when the initial write of a request
is not complete.

PR 10038, 38861, 39679
Submitted by: Patrick McManus <mcmanus datapower.com> (in 2003)
              Stefan Fleiter <stefan.fleiter web.de>  (in 2006)
              and Davanum Srinivas (in 2006).  Committed patch
              contains parts of all three, tweaked by Roy (2008).

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@655637 13f79535-47bb-0310-9956-ffa450edef68