app/testpmd: fix synchronic port hotplug

app/testpmd: fix synchronic port hotplug

When the user uses the synchronic hot-plug commands, attach\detach, in
order to insert\remove a port from the system, the forward ports list
update is missed in the current implementation.

Thus, an invalid port may be used for data-path in case of detach
because the detached port was not removed from the forward port list.

In addition, a new port is not used for data-path in case of attach, as the
default behavior of Testpmd, because the attached port was not inserted
to the forward port list.

Update the forward port list in the above cases to allow the correct
port usage for data-path in the next packet forwarding start.

Fixes: edab33b1c01d ("app/testpmd: support port hotplug")
Cc: stable@dpdk.org
Signed-off-by: Matan Azrad <matan@mellanox.com>