[vitess-operator] add etcd example

[luismacosta]

[vitess-operator] add etcd example: provide an example to deploy EtcdLockserver

@frouioui Can you please review? Thank you.

[frouioui]

Hi @luismacosta, you have added this under the test directory. Operator examples are on the Vitess repository, and the tests for them can be found here under ./test/endtoend/. It would be good to have a test file that uses the manifest you're adding, so we know how to deploy it and run it, and so that it can be used in the examples found on the Vitess repository.