Was using a closure for tag function thus storage variable was always
referencing the last value of the iteration.

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

Replaced all logger call in child.
Added dedicated libev loop.
Handle exceptions using fatal helpers of ForkedJob.

Usefull after fork.