* Two-step requests redirected to a DN
* Step 1) Submit a Http request with neither auto-redirect nor data.
* Step 2) Submit another Http request with the URL from the Location header
* with data.
* The reason of having two-step create/append is for preventing clients to
* send out the data before the redirect. This issue is addressed by the
* "Expect: 100-continue" header in HTTP/1.1; see RFC 2616, Section 8.2.3.
* Unfortunately, there are software library bugs (e.g. Jetty 6 http server
* and Java 6 http client), which do not correctly implement "Expect:
* 100-continue". The two-step create/append is a temporary workaround for
* the software library bugs.
* Also implements two-step connects for other operations redirected to
* a DN such as open and checksum