test: add some unit tests for channel passing
test: add some unit tests for channel passing

One of the tests currently fails.

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

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