Implement exec over the SPDY protocol

[admilazz]

This change adds improved exec support. The existing exec support uses web sockets, which has a flawed protocol leading to some commands running forever. This change helps address issue #397 .

I tried to replace the implementation of the existing exec support to provide a seamless upgrade. Unfortunately, many internal implementation details of the web socket approach (e.g. WebSocketNamespacedPodExecAsync, MuxedStream, StreamDemuxer, etc), were publicly exposed, and it would be a breaking change to remove them. I did replace the implementation of NamespacedPodExecAsync, however, which was generic enough.

This PR makes the following public API changes:

• The fluent API gains new members:
  • ExecCommandAsync - Execs the current resource, which does not necessarily have to be a pod
  • OpenSPDYAsync - Makes the request and upgrades it to a SPDY connection
  • OpenWebSocketAsync - Makes the request and upgrades it to a web socket connection

NOTE: This PR builds on and includes changes from two other PRs (#405 and #406). I'm not sure how best to represent that in a PR, but the files actually added or changed in this specific PR are:

• ByteBuffer.cs (to edit a comment)
• Kubernetes.ConfigInit.cs (to remove the automatic retry support added by the Microsoft.Rest.ClientRuntime)
• Kubernetes.Exec.cs (to replace the NamespacedPodExecAsync implementation)
• KubernetesRequest.cs (to add the three methods named above)
• PipeStream.cs
• SPDYExec.cs

[k8s-ci-robot]

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[admilazz]

/assign @krabhishek8260

[brendandburns]

I'll review this after the dependent PRs are merged.

[andykernahan]

@admilazz Are you planning to add tests for the new types and functionality? Similarly, the new SPDY.net dependency was only very recently created (by you under @AdamMil?) and is not tested.

[admilazz]

@admilazz Are you planning to add tests for the new types and functionality? Similarly, the new SPDY.net dependency was only very recently created (by you under @AdamMil?) and is not tested.

Yes, but as for the priority of it I will see what happens to the other PRs. This is way down the stack.

[admilazz]

I guess I'll put this in a separate project.

[k8s-ci-robot]

@admilazz: PR needs rebase.

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[admilazz]

the new SPDY.net dependency was only very recently created (by you under @AdamMil?) and is not tested.

P.S. I wouldn't say it's untested, though. :-) I did run 20,000 execs of various kinds in a row with zero failures... But it's true I haven't written unit tests yet.