incompatibility issues in setup

[aslom]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behavior:
follow https://redhat-developer-demos.github.io/knative-tutorial/knative-tutorial-serving/setup.html

kubectl get pods -n knative-serving
NAME                          READY   STATUS             RESTARTS   AGE
activator-8cb6d456-pfsbw      0/1     Running            2          81s
autoscaler-dd459ddbb-mgk7n    0/1     Running            1          81s
controller-8564567c4c-9pr46   0/1     CrashLoopBackOff   3          81s
webhook-7fbf9c6d49-lzjpj      0/1     CrashLoopBackOff   3          81s

k -n knative-serving logs controller-8564567c4c-9pr46
2020/06/13 21:42:00 Registering 4 clients
2020/06/13 21:42:00 Registering 4 informer factories
2020/06/13 21:42:00 Registering 13 informers
2020/06/13 21:42:00 Registering 7 controllers
{"level":"info","ts":"2020-06-13T21:42:00.337Z","caller":"logging/config.go:108","msg":"Successfully created the logger."}
{"level":"info","ts":"2020-06-13T21:42:00.337Z","caller":"logging/config.go:109","msg":"Logging level set to info"}
{"level":"info","ts":"2020-06-13T21:42:00.337Z","logger":"controller","caller":"profiling/server.go:59","msg":"Profiling enabled: false","commit":"f87352b"}
{"level":"fatal","ts":"2020-06-13T21:42:00.338Z","logger":"controller","caller":"sharedmain/main.go:335","msg":"Version check failed","commit":"f87352b","error":"kubernetes version \"1.15.0\" is not compatible, need at least \"1.15.1\" (this can be overridden with the env var \"KUBERNETES_MIN_VERSION\")","stacktrace":"knative.dev/serving/vendor/knative.dev/pkg/injection/sharedmain.CheckK8sClientMinimumVersionOrDie\n\tknative.dev/serving/vendor/knative.dev/pkg/injection/sharedmain/main.go:335\nknative.dev/serving/vendor/knative.dev/pkg/injection/sharedmain.MainWithConfig\n\tknative.dev/serving/vendor/knative.dev/pkg/injection/sharedmain/main.go:169\nknative.dev/serving/vendor/knative.dev/pkg/injection/sharedmain.MainWithContext\n\tknative.dev/serving/vendor/knative.dev/pkg/injection/sharedmain/main.go:133\nknative.dev/serving/vendor/knative.dev/pkg/injection/sharedmain.Main\n\tknative.dev/serving/vendor/knative.dev/pkg/injection/sharedmain/main.go:127\nmain.main\n\tknative.dev/serving/cmd/controller/main.go:34\nruntime.main\n\truntime/proc.go:203"}

Expected behavior
Installation work for serving

Screenshots
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Desktop (please complete the following information):

• OS: macOS
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.

[kameshsampath]

closed vi #225