Fix case_clause in enetconf_ssh; pass message id on parse error

enetconf_ssh:parse_xml expects to get a tuple with three arguments, one
being the message id.  Let's make sure it gets that, instead of causing
a case_clause error.

With this change, we can send error replies for incorrect requests
instead of just dropping the connection.
Merge pull request #9 from legoscia/report-parse-errors

Fix case_clause in enetconf_ssh; pass message id on parse error