Fix path validation and proxy initialization

Author: emgarten

src/Sleet/Util.cs

@@ -16,7 +16,10 @@ internal static void InitNetwork(LocalSettings settings)
             var proxySettings = settings?.Json?["proxy"] ?? new JObject();
             if (proxySettings["useDefaultCredentials"]?.ToObject<bool>() == true)
             {
-                WebRequest.DefaultWebProxy.Credentials = CredentialCache.DefaultCredentials;
+                if (WebRequest.DefaultWebProxy != null)
+                {
+                    WebRequest.DefaultWebProxy.Credentials = CredentialCache.DefaultCredentials;
+                }
             }
         }
 

src/SleetLib/FileSystem/AzureFileSystem.cs

@@ -24,7 +24,7 @@ public AzureFileSystem(LocalCache cache, Uri root, Uri baseUri, BlobServiceClien
             var expectedPath = UriUtility.EnsureTrailingSlash(root);
 
             // Verify that the provided path is sane.
-            if (!expectedPath.AbsoluteUri.StartsWith(expectedPath.AbsoluteUri, StringComparison.Ordinal))
+            if (!expectedPath.AbsoluteUri.StartsWith(containerUri.AbsoluteUri, StringComparison.Ordinal))
             {
                 throw new ArgumentException($"Invalid feed path. Azure container {container} resolved to {containerUri.AbsoluteUri} which does not match the provided URI of {expectedPath}  Update path in sleet.json or remove the path property to auto resolve the value if using a connection string.");
             }