Kubelet token distribution on Azure

[erictune]

Make #2387 work for AWS.

Suggested steps:

1. add a cluster/azure/templates/create-dynamic-salt-files.sh similar to cluster/gce/templates/create-dynamic-salt-files.sh, and add the code to util.sh to copy the salt-overlay files on top of salt.
2. add the same lines to cluster/azure/templates/create-dynamic-salt-files.sh as Kubelet talks securely to apiserver #2387 added to cluster/gce/templates/create-dynamic-salt-files.sh
3. change {% if grains.cloud == "gce" %} to {% if grains.cloud in ["gce", "azure"] %} in cluster/saltbase/salt/kube-apiserver/default and cluster/saltbase/salt/kube-apiserver/init.sls
4. change if provider != "gce" to if provider != "gce" and provider != "azure" in cmd/e2e/e2e.go
5. validate by running CLOUD_PROVIDER=azure hack/e2e-test.sh

[erictune]

At the same time as doing this work, also change the kube-proxy to set the flag:
--master=http://$APISERVER:7080.

[erictune]

Looking at the code, it appears this is fixed.