Was ignoring event 0 which is used to stop "polling" events.
Was using mapping which couldn't work with multiple events.

These jobs are needed for VM migration/clone.

Libvirt raises an exception saying "domain not runnning" when trying to destroy
a VM that is in fact running. So we try to figure out if this is this kind of
exception and we ignore it in this case.

Only log error in case of error.

When VM is not started, vnc port value is -1 in the libvirt domain XML config.

Some tags were returning None because of bad decorator.

Support for registering/unregistering sub object to the cc-server.
Support for tag lifecycle handling (libev), was previously managed by plugins.

Try to connect to libvirt while no exception is thrown.

Clean global variable for libvirt connection.

In case of error.

Plus error handling.

No more global variable.

Therefore do not block next stop actions.

Refactored plugins.
Updated hypervisor libvirt event handling.
Async rpc handling.
Minor renaming for libvirt event callback.
Remove uneeded method sub_tags (in hypervisor Handler).

Create/Start/Stop/Destroy/Undefine/Export/Suspend/Resume.