Fix bug 2071: create secret

Manually create a service-account-token secret
for service account when k8s cluster is created
in case k8s version >=1.24.

ServiceAccount object should be created first.
When deleting a k8s cluster. Corresponding
ServiceAccount and Secret are automatically
deleted as well.

In k8s < 1.24, secret is automatically created.

Change-Id: I160b1f87a64cf7a1bbb1fa8587259d8fbd3e6cd4
Signed-off-by: Patricia Reinoso <patricia.reinoso@canonical.com>