Validating vault settings / context (Azure#3360)

Fix for the issue#3331.
Checking vault context parameters before creating client to perform actual operation.

Author: sriramvu

src/ResourceManager/SiteRecovery/Commands.SiteRecovery/Common/PSSiteRecoveryClient.cs

@@ -312,6 +312,12 @@ public CustomRequestHeaders GetRequestHeaders(bool shouldSignRequest = true)
         /// <returns>Site Recovery Management client</returns>
         private SiteRecoveryManagementClient GetSiteRecoveryClient()
         {
+            if (string.IsNullOrEmpty(asrVaultCreds.ResourceName) ||
+                string.IsNullOrEmpty(asrVaultCreds.ResourceGroupName))
+            {
+                throw new InvalidOperationException(Properties.Resources.MissingVaultSettings);
+            }
+            
             SiteRecoveryManagementClient siteRecoveryClient =
                 AzureSession.ClientFactory.CreateCustomClient<SiteRecoveryManagementClient>(
                 asrVaultCreds.ResourceName,
@@ -426,4 +432,4 @@ public static T Deserialize(string xmlString)
             return propertyBagContainer;
         }
     }
-}
+}