network: drop back compat code loading actual bridge name

The actual network def was updated to save the bridge name back
in 1.2.11:

  commit a3609121
  Author: Laine Stump <laine@laine.org>
  Date:   Fri Nov 21 12:20:37 2014 -0500

    network: save bridge name in ActualNetDef when actualType==network too

The chance that someone is running libvirt < 1.2.11 and wants
todo a live upgrade to 5.3.0 without a host reboot is essentially
zero. We can thus reasonably drop the back compat code now.
Reviewed-by: NLaine Stump <laine@laine.org>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

src/network/bridge_driver.c

@@ -4832,17 +4832,6 @@ networkNotifyActualDevice(virNetworkPtr net,
         goto error;
     }
 
-    /* if we're restarting libvirtd after an upgrade from a version
-     * that didn't save bridge name in actualNetDef for
-     * actualType==network, we need to copy it in so that it will be
-     * available in all cases
-     */
-    if (actualType == VIR_DOMAIN_NET_TYPE_NETWORK &&
-        !iface->data.network.actual->data.bridge.brname &&
-        (VIR_STRDUP(iface->data.network.actual->data.bridge.brname,
-                    netdef->bridge) < 0))
-            goto error;
-
     /* see if we're connected to the correct bridge */
     if (netdef->bridge) {
         bool useOVS = false;