Integration test does not restore original kubectl context

[fredjywang]

To recreate:

1. Set up cluster according to CONTRIBUTING.md docs.
2. Run make integration-suite, which creates it's own kind cluster and sets its own context.
3. After a successful integration test, if you make clean then run make install again, you may get this error:

The connection to the server localhost:8080 was refused - did you specify the right host or port?

Can fix by resetting kubectl context with kind export kubeconfig --name my-cluster, but may be beneficial for integration to reset kubectl context for user.