[WIP] Use upstream DOMAIN_INTERFACE_ADDRESSES_SRC_AGENT

[MalloZup]

What does this PR:

In past we used domain.QemuAgentCommand for getting the Interfaces via qemu-agent.

• Now we are using domain.ListAllInterfaceAddresses(libvirt.DOMAIN_INTERFACE_ADDRESSES_SRC_LEASE

• additionally as you can see, we get more simpler codebase with the new function from upstream.

• for domains which are down we just skip. This was also the behaviour from libvirt-api

We still need a loop function with timeouts because otherwise we might endup in a situation where the QEMU-AGENT is installed but not already setup. So we need to wait and retry for a delay of time.

If we don't have the timeout with the loop we will get at 1st try error: Guest agent is not responding: QEMU guest agent is not connected

[dmacvicar]

I still don't see how the agent source is used.

[MalloZup]

OK everything is ok now

[dmacvicar]

@MalloZup can you please post an example of the configuration that would fail? (no need for it to be real, just an example, to understand it better)

[MalloZup]

i prefer to concetrate on other issues which will bring more value.
I think this feature would be a nice refactor but i am unsure about the qemu-agent, since at moment we don't tests it in testacc so we cannot assume this could bring a regression. ( all the tests i did were ok but i am maybe missing some complexity). So in this case i prefer to keep the old code that works instead of this refactor. ( which is nice but add some risk without a real gain of feature/values)