Add missing states in ServiceUpdateState (#2292)

Author: Nowheresly

docker-java-api/src/main/java/com/github/dockerjava/api/model/ServiceUpdateState.java

@@ -6,6 +6,9 @@
  * @since {@link RemoteApiVersion#VERSION_1_24}
  */
 public enum ServiceUpdateState {
+    @JsonProperty("unknown")
+    UNKNOWN,
+
     @JsonProperty("updating")
     UPDATING,
 
@@ -15,6 +18,12 @@ public enum ServiceUpdateState {
     @JsonProperty("completed")
     COMPLETED,
 
+    @JsonProperty("rollback_started")
+    ROLLBACK_STARTED,
+
+    @JsonProperty("rollback_paused")
+    ROLLBACK_PAUSED,
+
     @JsonProperty("rollback_completed")
     ROLLBACK_COMPLETED
 }