Allow to set attributes

[alxgomz]

It seems it is not possible at the moment the set element's attributes as the set_target function check if xpath is a node.
The goal would to set attributes like this:

xml:
    xmlstring: <Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" URIEncoding="UTF-8" redirectPort="8443"/>
    xpath: /Connector/@port
    value: 8081

That would be very useful i think.
If I missed something jus let me know.

[berenddeschouwer]

Duplicate of #15

[dagwieers]

The xml module is upstream now (and ships with Ansible v2.4).

Please close this issue, and if needed, open a new issue at: https://github.com/ansible/ansible/issues