If something goes wrong during the Azure cloud detection, trying to cast
the returned value will result in the following panic and give no clue
as to what the error was.
```
panic: interface conversion: cloudprovider.Interface is nil, not *azure.Cloud
goroutine 1 [running]:
k8s.io/kubernetes/test/e2e/framework/providers/azure.newProvider()
test/e2e/framework/providers/azure/azure.go:50 +0x2b5
k8s.io/kubernetes/test/e2e/framework.SetupProviderConfig({0xc0007966b8, 0x5})
test/e2e/framework/provider.go:82 +0x1a6
```