fix(interfaces): interface changes roll back as one, a running one is not deleted, each interface is read once

Plan reviewed with Codex; tried on a udev host (AlmaLinux 10) and a
netcf one (AlmaLinux 8).

- Changes are one change of the host's configuration (libvirt's
  interface change transaction): a bridge that does not start used to
  be undefined, leaving its member without the addresses and start
  mode the bridge took from it; now the whole change rolls back, the
  member's own configuration too, and so does a commit libvirt refuses.
  A rollback that fails too is reported with the failure, saying the
  host's configuration may be changed.
  Deleting a bridge, which defines its
  members again on their own, is one change as well.
- A running interface is not deleted: the page hid Delete, but a post
  deleted it. A bridge with addresses and several members is refused
  (which member takes the addresses is the user's choice); the
  confirmation says that its members are defined again.
- A bridge takes only a device in no bridge, bond or VLAN as the host
  has them configured, at any depth (a bridge's bond's devices), not
  the loopback, a libvirt network's bridge or a VM's tap; an ethernet
  interface configures only such a device too.
- Whether the host can change interfaces: unsupported or refused by
  its access rules is a no, bad XML a yes, anything else (the
  connection, the login) is raised instead of taken for a yes. A page
  whose host could not be read offers no actions.
- Reads: the list reads each interface's XML once from one listing
  (listAllInterfaces: every state, not the active and the defined ones
  apart); a page reads the running and the saved definition once each
  (cached_property). netcf writes a link speed of -1 for a card that
  has none (a virtio one) and then refuses its own XML: the saved one
  is read instead, where virsh and the page failed. Name and MAC come
  from libvirt's object, without a call. Each family says how it is
  addressed (DHCP, autoconf, static or none) and every address, its
  prefix where it has one; no
  address is not "DHCP" any more. A bridge's members carry their link
  state and speed; an unknown speed (0, -1, 4294967295) is none.
- The interface API lists from the same reader. get_details,
  get_bridge, get_bridge_slave_ifaces and the per-family getters go.

interfaces/api/viewsets.py

@@ -3,7 +3,7 @@ from django.shortcuts import get_object_or_404
 from computes.models import Compute
 from rest_framework import viewsets
 from rest_framework.response import Response
-from vrtManager.interface import wvmInterfaces, wvmInterface
+from vrtManager.interface import wvmInterfaces
 
 from .serializers import InterfacesSerializer
 
@@ -17,15 +17,10 @@ class InterfaceViewSet(viewsets.ViewSet):
     serializer_class = InterfacesSerializer
     
     def list(self, request, compute_pk=None):
-        queryset = []
         compute = get_object_or_404(Compute, pk=compute_pk)
         
         conn = wvmInterfaces(compute.hostname, compute.login, compute.password, compute.type)
-        ifaces = conn.get_ifaces()
-
-        for iface in ifaces:
-            interf = wvmInterface(compute.hostname, compute.login, compute.password, compute.type, iface)
-            queryset.append(interf.get_details())
+        queryset = conn.get_ifaces_info()
 
         serializer = InterfacesSerializer(queryset, many=True, context={'request': request})