tools/xenstored: delay_request: don't assume conn->in == in

tools/xenstored: delay_request: don't assume conn->in == in

delay_request() is currently assuming that the request delayed is
always conn->in. This is currently correct, but it is a call for
a latent bug as the function allows the caller to specify any request.

To prevent any future surprise, check if the request delayed is the
current one.

Fixes: c5ca1404b4 ("tools/xenstore: add support for delaying execution of a xenstore request")
Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
Reviewed-by: Juergen Gross <jgross@suse.com>