When libvirt daemon is restarted, qubesd attempt to re-connect to the
new instance transparently (through virConnect object wrapper). But the
code lacked re-registering event handlers.
Fix this by adding reconnect callback argument to virConnectWrappper, to
be called after new connection is established. This callback will
additionally get old connection as an argument, if any cleanup is
needed. The old connection is closed just after callback returns.
Use this to re-register event handler, but also unregister old handler
first. While full unregister wont work on since old libvirt daemon
instance is dead already, it will still cleanup client structures.
Since the old libvirt connection is closed now, adjust also domain
reconnection logic, to handle stale connection object. In that case
isAlive() call throws an exception.
FixesQubesOS/qubes-issues#5303
8e36a2ac61