stronger validation for tls termination type

[pweil-]

This strengthens the validation on the api server side for routes to protect against a bad tls termination type string. The router correctly ignored it but you could still create it and it was unclear why the router didn't work.

/cc @jcantrill

[vagrant@openshiftdev origin]$ cat ~/test_route.json 
{
    "apiVersion": "v1beta1",
    "kind": "Route",
    "metadata": {
        "labels": {
            "generatedby": "OpenShiftWebConsole",
            "name": "ruby-hello-world"
        },
        "name": "ruby-hello-world"
    },
    "serviceName": "ruby-hello-world",
    "tls": {
        "termination": "unsecure"
    }
}
[vagrant@openshiftdev origin]$ osc create -f ~/test_route.json 
Error: route "ruby-hello-world" is invalid: tls.termination: invalid value 'unsecure': invalid value for termination, acceptable values are edge, passthrough, reencrypt, or emtpy (no tls specified)

[pweil-]

[test]

[openshift-bot]

continuous-integration/openshift-jenkins/test SUCCESS (https://ci.openshift.redhat.com/jenkins/job/test_pull_requests_openshift3/1842/)

[smarterclayton]

LGTM [merge]

[openshift-bot]

continuous-integration/openshift-jenkins/merge SUCCESS (https://ci.openshift.redhat.com/jenkins/job/merge_pull_requests_openshift3/1597/) (Image: devenv-fedora_1291)

[openshift-bot]

Evaluated for origin up to 5b735e9