Automatic merge from submit-queue

Node Conformance & E2E: Get node name from node object.

This PR changes the node e2e test framework to get node name from apiserver instead of test flags.

When a user tried out the node conformance test, he found that node conformance test will not work properly if kubelet is started with `hostname-override`.

The reason is that node conformance test is using [the default node name - `os.Hostname`](https://github.com/kubernetes/kubernetes/blob/master/test/e2e_node/e2e_node_suite_test.go#L124), which may be different from `hostname-override`. This will cause test pods not scheduled, and eventually test timeout.

We can expose a flag from node conformance test, and let user set node name themselves if they are using `hostname-override` on kubelet. However, let the framework automatically detect it from apiserver is more user friendly.

/cc @kubernetes/sig-node 
This PR 1) only changes node e2e test framework; 2) fixes a problem in node conformance test which is a 1.5 feature. @saad-ali Can we have this in 1.5?