init-xenstore-domain: cleanup all resources on a single exit path

init-xenstore-domain: cleanup all resources on a single exit path

Previously xs_fd would be left open, which is CID 1055993 (previously
partially fixed by 3bca826aae5eb).

Instead arrange for both success and error cases to cleanup everything
on a single exit path instead of doing partial cleanup on the success
path a few operations higher up.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>