Libvirt doesn't like null handler id or timer id. Start the count to 1.

With the permission of Romain Degez, CTO of Smartjog.

Signed-off-by: Sébastien Luttringer <sebastien.luttringer@smartjog.com>

Moved to cc-common

hypervisor/__init__.py ->
    hypervisor/__init__.py (Handler)
    hypervisor/kvm.py (Hypervisor -> KVM)
    hypervisor/lib.py (Storage*/Volume)

This prevents client libvirt version 0.8.8 to segfault when reseting libvirt
event handlers.

This is a fix when is the same poll we try to update a tag value for a VM and
the domain just has been removed.

Harmless renaming.

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

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.

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

TODO: Need to handle event.

Basic support.