tests: Unset ns_path when deleting the netns

The cleaning is condition on this variable being set. So let's unset it
after we clean the resources.

Signed-off-by: Rodrigo Campos <rodrigo@amutable.com>

tests/integration/checkpoint.bats

@@ -30,6 +30,9 @@ function delete_netns() {
 
 	# Delete the namespace only if the ns_name variable is set.
 	[ -v ns_name ] && ip netns del "$ns_name"
+
+	unset ns_name
+	unset ns_path
 }
 
 function setup() {

tests/integration/netdev.bats

@@ -20,6 +20,9 @@ function setup_netns() {
 function delete_netns() {
 	# Delete the namespace only if the ns_name variable is set.
 	[ -v ns_name ] && ip netns del "$ns_name"
+
+	unset ns_name
+	unset ns_path
 }
 
 function setup() {