commit 52d064f4 added
VIR_NETWORK_XML_INACTIVE in order to allow suppressing the
auto-generated list of VFs in network definitions, and a --inactive
flag to virsh net-dumpxml to take advantage of the flag. However, it
missed out on two opportunities:

1) Use INACTIVE to get the current config of the network as it
   exists on disk, rather than the currently active config.

2) Add INACTIVE to the flags used for the virsh net-edit command, so
   that it won't include the forward-pool interfaces that were
   autogenerated, and so that a re-edit of the network prior to
   restarting it will show any other edits made since the last restart
   of the network. (prior to this patch, if you edited a network a 2nd
   time without restarting, all of the previous edits would magically
   disappear).

In order to fit with the new #define-based generic edit function in
virsh.c, a new function vshNetworkGetXMLDesc() was added. This
function first tries to call virNetworkGetXMLDesc with the INACTIVE
flag added, then retries without if the first attempt fails (in the
manner expected when the server doesn't support it).