Write error log when deployed to cloud and default service information is used

[TimHess]

Due to the changes in connectors to separate out Cloud Foundry functionality, some Steeltoe users are struggling with service bindings in cloud hosted scenarios because they don't realize they need another package reference.

In order to improve this experience, (at a minimum for Eureka on Cloud Foundry), write error logs if service bindings aren't detected but are effectively required.

• Use Platform.IsCloudHosted or Platform.IsCloudFoundry to detect running on the cloud
• Log errors if/when default service connection values are used (eg: http://localhost:8761)
• This change might go best in EurekaDiscoveryClientExtension or EurekaPostConfigurer

[TimHess]

Logging isn't going to be very natural (or appropriate) where this needs to run (services.PostConfigure<T>(...)) so this is probably going to be best accomplished by throwing an exception, which isn't ideal but still seems valid to me