panic on the Read func
Fixes#8995
The Diagnostics profile was a badly laid out resource. All we needed to
set was whether it was enabled and the storage account to save the logs
to. The old schema parameter was deprecated and replaced with a much
simplier structure
```
% make testacc TEST=./builtin/providers/azurerm TESTARGS='-run=TestAccAzureRMVirtualMachine_diagnosticsProfile'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2016/09/29 12:21:04 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/azurerm -v
-run=TestAccAzureRMVirtualMachine_diagnosticsProfile -timeout 120m
=== RUN TestAccAzureRMVirtualMachine_diagnosticsProfile
--- PASS: TestAccAzureRMVirtualMachine_diagnosticsProfile (1066.76s)
PASS
ok
github.com/hashicorp/terraform/builtin/providers/azurerm1066.776s
```