Decoupling libvirtconnection.py from clientIF.py

1.) Decoupling libvirtconnection.py from clientIF.py
adding libvirt cb handlers for vm events belongs in vm.py
2.) bugfix: not all libviryconnecition.get() invocations
from vdsm are wrapped with error handling code
(with an important implication in the bug description:
 causes vdsm to shutdown on libvirt connection error)

These two come in the same patch because removing
the cif dependency (clientIF instance) from libvirtconnection
must handle errors in a new way - sendind SIGTERM to the current
process which solves the bug.

Change-Id: Ibc550ea40ebb3abcf37ebfa59cbf8df8e42daa96
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=958367
Signed-off-by: Mooli Tayer <mtayer@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/16393
Reviewed-by: Dan Kenigsberg <danken@redhat.com>