Support disabled storage account public access.

> Please provide us with the following information:
> ---------------------------------------------------------------

### This issue is for a: (mark with an `x`)
```
- [ ] bug report -> please search issues before submitting
- [x] feature request
- [ ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)
```

### Minimal steps to reproduce
>
create a blockchain workbench.
open app the app page.
upload the HelloBlockchain.json and HelloBlockchain.sol files.
Disable the Blob public access of storage account in blockchain workbench resource group
create a new contract with any description.

### Any log messages given by the failure
>
In blockchain workbench Website.
The message would be
This may take some time. Your administrator can use RequestId **** to look up details in Application Insights.

checker docker log in ScaleSet
Would find something like
[10:25:11 INF] {SourceContext="TransactionProcessor", ServiceName="eth-watcher"} Processing transaction with 1 events
[10:25:11 ERR] {SourceContext="BlockProcessor", ServiceName="eth-watcher"} Encountered exception during block processing after 5 tries, SKIPPING block number 191027: System.Net.Http.HttpRequestException: Response status code does not indicate success: 409 (Public access is not permitted on this storage account.).
at System.Net.Http.HttpResponseMessage.EnsureSuccessStatusCode()
at System.Net.Http.HttpClient.GetStringAsyncCore(Task`1 getTask)

### Expected/desired behavior
>
Hope could support disabled storage account public access.
Actually, There is all necessary information in key vault.
The blockchainworkbenchprod.azurecr.io/eth-watcher could support access storage account disabled public(anouymous) access.

### OS and Version?
> Windows 7, 8 or 10. Linux (which distribution). macOS (Yosemite? El Capitan? Sierra?)

### Versions
>
1.8.1
### Mention any other details that might be useful

> ---------------------------------------------------------------
> Thanks! We'll be in touch soon.