VmMetadataApiHandler should be only used on VM

[saugereau]

Is your feature request related to a problem? Please describe.
Using Cosmosdb SDK on ContainerApp, I can observe that http://169.254.169.254/metadata/instance?api-version=2020-06-01 is unsuccessfully called with a timeout of 1 min. Because the endpoint doesn't exist on containerapp environment ...it shouldn't be called

Describe the solution you'd like
The metadata instance endpoint should be called only for VM not containerapp, or should be configurable.

[Pilchie]

You can opt out of this call by setting an environment variable: COSMOS_DISABLE_IMDS_ACCESS

See #4568 for details.