Discover without credentials

[dadoonet]

When a Node is running Inside Azure platform, it sounds like new Azure API added by #63 supports API calls without the need to provide credentials. Let see if we can use that and simplify (a lot) the VM creation process.

update

Note that for now, Azure only supports authentication using:

• certificates (that's what we are using for now)
• Active Directory

See https://msdn.microsoft.com/en-us/library/azure/ee460782.aspx

Feature request opened Azure/azure-sdk-for-java#464

Another option in the feature could be using tokens instead of certificate. See Azure/azure-sdk-for-java#456

[dadoonet]

This issue was moved to elastic/elasticsearch#12698