sch_plug can be used to perform functional qdisc unit tests
controlling explicitly the queuing behaviour from user-space.
Plug support lacks since its introduction in 2012. This change
introduces basic support, to control the tc status.
v1 -> v2:
- use the SPDX identifier
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David Ahern <dsahern@gmail.com>
