The read() in apr_recv() would always be called first and return EAGAIN.

This one change to eliminate the read unless there are really bytes to read
is good for a 7 to 9% performance boost on AIX.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@89809 13f79535-47bb-0310-9956-ffa450edef68