If TCP is passed in as the protocol, by default, we add TCP as the
protocol within the Kubernetes or OpenShift artifacts.
By default, TCP is already selected within Kubernetes and thus having
the TCP output is redundant.
This commit checks to see if TCP has already been selected, and if it
has, ignores adding it to the list of ports.
Closes https://github.com/kubernetes-incubator/kompose/issues/392
