Fix the Cohttp_posix_io.Unbufferd_IO header parsing
Fix the Cohttp_posix_io.Unbufferd_IO header parsing

The unit test now passes.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@eu.citrix.com>

johnelse/xcp-idl,xapi-project/message-switch,euanh/xcp-idl,xapi-project/message-switch,djs55/xcp-idl,Chunjie/xcp-idl,xapi-project/message-switch