Weave support

[bodom0015]

Problem

There is no current configuration option for selecting the desired type of Pod Network.

Approach

This PR adjusts init-master.bash to accept a pod_network_type. Currently supported options are flannel or weave.

NOTE: Flannel will be deployed by default.

How to test

1. Execute git clone https://github.com/nds-org/kubeadm-bootstrap && cd kubeadm-bootstrap/ to clone the repo
2. Execute sudo ./install-kubeadm.bash to install kubeadm
3. Execute sudo -E ./init-master.bash weave to bootstrap master with weave support
   • If no argument is given, flannel will be chosen by default
4. After everything is up, execute kubectl get pod -n kube-system
   • You should see that weave is now running instead of flannel