Ensure tests which rely on SSH behavior are skipped if unavailable

A number of tests rely on SSH behavior but are not marked with
SkipUnlessSSHKeysPresent(). This means that the tests will run and
hang. This can be confusing for users because they may not know why
the tests failed. Instead, we should be reporting on the known issue
and skipping the test (hence why the helper Skip... function exists).

test/e2e/node/node_problem_detector.go

@@ -56,6 +56,8 @@ var _ = SIGDescribe("NodeProblemDetector [DisabledForLargeClusters]", func() {
 	})
 
 	ginkgo.It("should run without error", func() {
+		framework.SkipUnlessSSHKeyPresent()
+
 		ginkgo.By("Getting all nodes and their SSH-able IP addresses")
 		nodes := framework.GetReadySchedulableNodesOrDie(f.ClientSet)
 		gomega.Expect(len(nodes.Items)).NotTo(gomega.BeZero())