…g Host and VirtualNetwork attributes accordingly

Signed-off-by: Felix Franz <[email protected]>

…e safe

* http://docs.opennebula.org/5.8/operation/references/host_states.html#list-of-states
* http://docs.opennebula.org/5.0/operation/host_cluster_management/host_guide.html#host-lifecycle

…rsion to '4.15.2'

Emacs complains that `UTF-8` (all uppercase) is not a valid name of a
coding system:

    Warning (mule): Invalid coding system ‘UTF-8’ is specified
    for the current buffer/file by the :coding tag.
    It is highly recommended to fix it before writing to a file.

Using the lowercase version solves the problem.

This fixes a few spurious errors I've found while using `python-oca`
with the Ansible module `one_vm`:

* The `except socket.error, e` syntax is deprecated since long and has
  been removed in Py3.

* On failure, ONE RPC seems to return a 4-tuple with the error message
  in position 1 and the constant `-1` in position 3.  This would have
  generated a `ValueError` which discarded the error message,
  obscuring important information.

* In general, try to be more verbose and precise in reporting errors
  to the caller.