Fixing Key Vault PS (get/set secret) APIs to work irrespective of the case of AzureKeyVaultDnsSuffix (property of AzureRmEnvironment).

Author: Kapil Jain

src/ResourceManager/KeyVault/Commands.KeyVault/Models/VaultUriHelper.cs

@@ -50,7 +50,7 @@ private Uri CreateAndValidateVaultUri(string vaultAddress)
                 throw new ArgumentException(string.Format(KeyVaultProperties.Resources.InvalidVaultUri, vaultAddress, this.KeyVaultDnsSuffix));
 
             if (vaultUri.HostNameType != UriHostNameType.Dns ||
-                !vaultUri.Host.EndsWith(this.KeyVaultDnsSuffix))
+                !vaultUri.Host.EndsWith(this.KeyVaultDnsSuffix, StringComparison.OrdinalIgnoreCase))
                 throw new ArgumentException(string.Format(KeyVaultProperties.Resources.InvalidVaultUri, vaultAddress, this.KeyVaultDnsSuffix));
 
             return vaultUri;