Updated documentation to reflect need for zone_type parameter when creating a zone

[racingferret]

With the inclusion of private DNS zones to the SDK, the documentation needs to reflect the additional parameter required when defining a zone. Following the documentation in the examples results in the following exception:

...
File "/usr/local/lib/python2.7/dist-packages/azure/mgmt/dns/operations/zones_operations.py", line 100, in create_or_update
body_content = self._serialize.body(parameters, 'Zone')
File "/usr/local/lib/python2.7/dist-packages/msrest/serialization.py", line 475, in body
raise errors[0]
msrest.exceptions.ValidationError: Parameter 'Zone.zone_type' can not be None.

[azuresdkci]

Can one of the admins verify this patch?

[codecov-io]

Codecov Report

Merging #2232 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2232   +/-   ##
=======================================
  Coverage   52.12%   52.12%           
=======================================
  Files        5625     5625           
  Lines      134589   134589           
=======================================
  Hits        70155    70155           
  Misses      64434    64434

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[lmazuel]

Hi @racingferret
You're totally right, but this is the RC client. And this sample has moved here (which needs to be adapted as well):
https://docs.microsoft.com/en-us/python/api/overview/azure/dns?view=azure-python

Since preview clients are installed only if "--pre" is provided, I prefer to keep the sample in sync with latest stable for now. But definitely keep your PR.
Thanks for your contribution!

[lmazuel]

DNS 2.0.0 will be released in a few seconds, so merge it now.
Thanks @racingferret again for the PR!