Fix the Disable-AzureRmVmssDiskEncryption issue.

[hyonholee]

The issue is that Disable-AzureRmVmssDiskEncryption incorrectly throws an error when the disk encryption extension is not the first extension of the VMSS.

Description

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[cormacpayne]

@hyonholee Hey Hyonho, would you mind updating the Compute change log with a snippet about this change you are making? Also, are we able to add any test coverage for this? It looks like it should be easy to mock out if setup would be too difficult.

[hyonholee]

@cormacpayne I added a test and updated change log.

[cormacpayne]

@hyonholee one quick comment

[cormacpayne]

@hyonholee are we checking anything with this resulting string, or are we just ensuring that an error is not thrown when the disk encryption extension is not the first extension?

[hyonholee]

@cormacpayne the test runs successfully if the error is not thrown when the disk encryption is not the first extension. Without the fix, this test fails with an exception thrown.

[cormacpayne]

@hyonholee thanks for the clarification, LGTM