Revisit default pipeline definition

[chlowell]

The default pipeline defined in PipelineClient needs some revision. In particular, it doesn't include a proxy policy, and the authentication policy may belong after the retry policy.

[xiangyan99]

We need to review before we update code

[johanste]

All pipelines should include a proxy policy. This includes management/control plane/autogenerated clients. And, yes the authentication policy should be after the retry policy.

[xiangyan99]

Fixed