Tag conformance tests with a [Conformance] string in the description

- remove skip list from conformance-test.sh and filter by the new tag
- remove experimental api tests from conformance test suite
- remove all tests from conformance test suite which are either
  restricted to e.g. gce, gke, aws or require SSH

test/e2e/host_path.go

@@ -59,7 +59,7 @@ var _ = Describe("hostPath", func() {
 		}
 	})
 
-	It("should give a volume the correct mode", func() {
+	It("should give a volume the correct mode [Conformance]", func() {
 		volumePath := "/test-volume"
 		source := &api.HostPathVolumeSource{
 			Path: "/tmp",
@@ -76,7 +76,7 @@ var _ = Describe("hostPath", func() {
 			namespace.Name)
 	})
 
-	It("should support r/w", func() {
+	It("should support r/w [Conformance]", func() {
 		volumePath := "/test-volume"
 		filePath := path.Join(volumePath, "test-file")
 		retryDuration := 180