rgw: some user metadata fixes

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: skeleton for obj copy across regions

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: bucket metadata, ignore ENOENT on put

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>
rgw: format put request auth

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>