selftests: forwarding: mirror_vlan: Uninstall trap

Instead of installing a trap before tests run and uninstalling it after
they run, mirror_vlan.sh installs it twice due to a typo. Fix the typo.
Signed-off-by: NPetr Machata <petrm@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

tools/testing/selftests/net/forwarding/mirror_vlan.sh

@@ -108,7 +108,7 @@ test_all()
 
 	tests_run
 
-	trap_install $h3 ingress
+	trap_uninstall $h3 ingress
 	slow_path_trap_uninstall $swp1 egress
 	slow_path_trap_uninstall $swp1 ingress
 }