http: simplify http_init_request

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
http: fix a segfault if DOCUMENT_URI is NULL string

Current code will segfault if we don't specify DOCUMENT_URI in nginx conf file.

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
http: parse CONTENT_LENGTH only when necessary

This will remove the unnecessary setting conent length for 'get' operation

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
sheep: remove unnecessary assignment in peer_read_obj

There is currently no client using the rsp->obj.copies. Since this assignment
is in the hottest code path, it is beneficial to remove it.

Signed-off-by: Liu Yuan <namei.unix@gmail.com>
Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>