user -> username in the mysql secret and references to it (#370)
user -> username in the mysql secret and references to it (#370)

Running kubedb 0.9.0, the secret has the keys `username` and `password` although the docs say that the key for the username is `user`. This PR updates the references to the username from `user` to `username` to reflect what it is actually called.
k8sdb/cli,k8sdb/cli,k8sdb/cli