Add fallback to 24h time format when MSI authentication fails due to date format mismatch

[vladkun]

Addressing this bug - #1135
Proper solution for the problem would be to use unix timestamps instead of some locale-dependent string representation of date for expires_on field, but since it would be breaking change for existing users, I propose to add fallback logic to allow MSI work on Linux machines. Tests include actual responses from MSI endpoints.

[msftclas]

All CLA requirements met.

[ulvii]

Hi @walk0r ,
Thank you for the contribution.
We are currently waiting for Azure side changes that might affect the behavior of the driver, we will revisit your PR once the changes are official.

[peterbae]

Hi @walk0r, thanks for your contribution. I've contacted the Azure team and confirmed that the String format for MSI expiry time being different across region/Azure Web App platform is a bug on Azure's side, and no changes should be necessary from the driver's end once the fix is merged in around Feb/Mar timeline. In the meantime, I've provided our driver with a temporary fix for this solution in the original issue #1135. I'll keep this PR open for now, and I will look to close it once the Azure fix is deployed and confirms that the driver doesn't need any code changes.

[vladkun]

@peterbae sure, I'm ok with it.