testsuite: release resources when vswitch exits.

testsuite: release resources when vswitch exits.

This change the testsuite macro to release the resources
configured by ovs-vswitchd when exiting as it used to be.

Fixes: 0f28164be02ac ("netdev-linux: make tap devices persistent")
Fixes: fe13ccdca6a22 ("vswitchd: Add --cleanup option to the 'appctl
                       exit' command")

Reported-by: Eric Garver <e@erig.me>
Signed-off-by: Flavio Leitner <fbl@redhat.com>
Signed-off-by: Joe Stringer <joe@ovn.org>