First cut at a "conformance test".

A conformance test is a test you run against a cluster that is already
set up.  We would use it to test a hosted kubernetes service to make
sure that it meets a bar for quality.  Also, a getting-started-guide
author, who has not implemented a complete set of cluster/...
scripts (that is, the getting-started-guide has some non-automated steps)
can use this to see which e2e tests pass on a cluster.

To be done in future PRs:
- disable tests which can't possibly run in a conformance test
  because they require things like cluster ssh.
- document that when we accept a getting-started-guide, that
  people should run the conformance test against their cluster
  (unless they already have cluster/... scripts.

I ran this against a GCE cluster and 22 tests passed.

cmd/e2e/e2e.go

@@ -51,7 +51,7 @@ func main() {
 	util.InitFlags()
 	goruntime.GOMAXPROCS(goruntime.NumCPU())
 	if *provider == "" {
-		glog.Error("e2e needs the have the --provider flag set")
+		glog.Info("The --provider flag is not set.  Treating as a conformance test.  Some tests may not be run.")
 		os.Exit(1)
 	}
 	if *times <= 0 {