virnetlink: Provide stub for virNetlinkBridgeVlanFilterSet()
In virnetlink.c there are two sections: the first one when
building WITH_LIBNL support, the other that provides stubs for
functions declared in the corresponding header file when building
without netlink support. But the stub implementation for
virNetlinkBridgeVlanFilterSet() was missing.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com> Reviewed-by: Peter Krempa <pkrempa@redhat.com>