network: Don't use ERR_NO_SUPPORT for invalid net-update requests
network: Don't use ERR_NO_SUPPORT for invalid net-update requests

VIR_ERR_NO_SUPPORT maps to the error string

    this function is not supported by the connection driver

and is largely only used for when a driver doesn't have any
implementation for a public API. So its usage with invalid
net-update requests is a bit out of place. Instead use
VIR_ERR_OPERATION_UNSUPPORTED which maps to:

    Operation not supported

And is what qemu's hotplug routines use in similar scenarios

fabianfreyer/libvirt,jfehlig/libvirt,olafhering/libvirt,jardasgit/libvirt,crobinso/libvirt,VenkatDatta/libvirt,eskultety/libvirt,zippy2/libvirt,andreabolognani/libvirt,VenkatDatta/libvirt,crobinso/libvirt,taget/libvirt,nertpinx/libvirt,eskultety/libvirt,andreabolognani/libvirt,datto/libvirt,datto/libvirt,zippy2/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,olafhering/libvirt,zippy2/libvirt,libvirt/libvirt,taget/libvirt,jfehlig/libvirt,andreabolognani/libvirt,datto/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,crobinso/libvirt,crobinso/libvirt,jfehlig/libvirt,eskultety/libvirt,nertpinx/libvirt,taget/libvirt,andreabolognani/libvirt,jfehlig/libvirt,nertpinx/libvirt,libvirt/libvirt,olafhering/libvirt,taget/libvirt,jardasgit/libvirt,eskultety/libvirt,jardasgit/libvirt,eskultety/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,libvirt/libvirt,datto/libvirt,jardasgit/libvirt,zippy2/libvirt,libvirt/libvirt,nertpinx/libvirt,datto/libvirt,olafhering/libvirt,nertpinx/libvirt,andreabolognani/libvirt,taget/libvirt