Bring Kubernetes 1.15

Bring Kubernetes 1.15

This change brings K8s 1.15 to Nordix. Some notes about
K8s 1.15 support of engine.
- The support is only included for the scenario k8-calico-nofeature.
- Deployment with the scenario k8-multus-plugins fails and
other scenarios are not tested since they may not be relevant
for us anymore. Due to this those scenarios have been removed from
1.15 branch.
- Installer, infra/installer/kubespray, 1.15 branch is tracked by
this branch.

An example command to deploy K8s 1.15 in online mode with the engine is.

- clone engine repo as usual
- cd engine/engine
- ./deploy.sh -s kubernetes -b 1.15 -c k8-calico-nofeature \
    -p <path to pdf> -i <path to idf> -v

If you are deploying on OpenStack using Heat, you need to
- specify the location of openrc file
- pass heat environment file as pdf

An example command to package K8s 1.15 for offline deployment with the
engine is.

- clone engine repo as usual
- cd engine/engine
- ./package.sh -s kubernetes -b 1.15 -v

Change-Id: Ic594b74780b6cdc309e36c24cea75e8e60863b2b