Add top-level error labels to write concern error (#766)

This will allow the driver to properly retry writes that the server
has labeled as a RetryableWriteError.

JAVA-4244

Author: jyemin

driver-core/src/main/com/mongodb/internal/connection/ProtocolHelper.java

@@ -243,7 +243,14 @@ public static MongoException createSpecialException(final BsonDocument response,
         } else if (errorMessage.contains("not master") || NOT_MASTER_CODES.contains(errorCode)) {
             return new MongoNotPrimaryException(response, serverAddress);
         } else if (response.containsKey("writeConcernError")) {
-            return createSpecialException(response.getDocument("writeConcernError"), serverAddress, "errmsg");
+            MongoException writeConcernException = createSpecialException(response.getDocument("writeConcernError"), serverAddress,
+                    "errmsg");
+            if (writeConcernException != null && response.isArray("errorLabels")) {
+                for (BsonValue errorLabel : response.getArray("errorLabels")) {
+                    writeConcernException.addLabel(errorLabel.asString().getValue());
+                }
+            }
+            return writeConcernException;
         } else {
             return null;
         }