[AKS] try to ensure kube config file has secure perms

[mboersma]

az aks get-credentials would create the ~/.kube/config file with permission for others to read and write it. This instead creates the file with 0600 permissions on non-Windows platforms, and warns the user if an existing config file doesn't have those permissions.

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[promptws]

View a preview at https://prompt.ws/r/Azure/azure-cli/6399
This is an experimental preview for @microsoft users.

[codecov-io]

Codecov Report

Merging #6399 into dev will not change coverage.
The diff coverage is n/a.

@@         Coverage Diff         @@
##           dev   #6399   +/-   ##
===================================
  Coverage    0%      0%           
===================================
  Files       11      11           
  Lines      133     133           
  Branches     9       9           
===================================
  Misses     133     133

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[mboersma]

I rebased against master but I'm still seeing a failure in Travis CI. Any ideas?

The following modules have invalid versions:
azure-cli-core
azure-cli

Update: never mind, I see #6407.

[williexu]

@mboersma I see you saw #6407
Just rebase again and you should get the update :)

[mboersma]

@williexu could this get reviewed soon? I'd like to get this bug fix in the next az release.