Backend: improve CloudFlare err detection

Update error code detection function in EtherServer to
recognize another possible pattern: " XXX." where XXX is
error code in question.

This is needed to process error messages like this:
```
Example error message: "Response status code does not indicate success: 520."
```

Fixes https://nblockchain.sentry.io/issues/5511801428/

src/GWallet.Backend/Ether/EtherServer.fs

@@ -82,6 +82,7 @@ module Server =
 
     let HttpRequestExceptionMatchesErrorCode (ex: Http.HttpRequestException) (errorCode: int): bool =
         ex.Message.StartsWith(SPrintF1 "%i " errorCode) || ex.Message.Contains(SPrintF1 " %i " errorCode)
+            || ex.Message.Contains(SPrintF1 " %i." errorCode)
 
     let exMsg = "Could not communicate with EtherServer"
     let PerformEtherRemoteCallWithTimeout<'T,'R> (job: Async<'R>): Async<'R> = async {