Never override the hostname on AWS nodes

[mrIncompetent]

What this PR does / why we need it:
Never override the hostname on AWS nodes.
Kube-Proxy uses the hostname= to lookup the corev1.Nodeobject its running on. On AWS nodes, the name of thecorev1.Node` is always the private dns name in AWS.
This is a requirement of the AWS code in kubernetes. Thus, manually overriding the hostname in the OS is not useful.
Instead if leads to the error messages:

W1023 13:23:23.835678       5 server.go:601] Failed to retrieve node info: nodes "aws-coreos-1-10-8-node-2" not found
W1023 13:23:23.835871       5 proxier.go:306] invalid nodeIP, initializing kube-proxy with 127.0.0.1 as nodeIP

NONE

[alvaroaleman]

/lgtm

[kubermatic-bot]

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This pull-request has been approved by: alvaroaleman, mrIncompetent

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