If BuildImage fails but logs something about success, don't succeed (#…

…2305)

This patch ensures that if the docker build commands result in logging
the string "Successfully built", the callback from that build will still
fail if there was an error in building.

Fixes #2184

docker-java-api/src/main/java/com/github/dockerjava/api/command/BuildImageResultCallback.java

@@ -67,14 +67,14 @@ public String awaitImageId(long timeout, TimeUnit timeUnit) {
     }
 
     private String getImageId() {
-        if (imageId != null) {
-            return imageId;
+        if (error != null) {
+            throw new DockerClientException("Could not build image: " + error);
         }
 
-        if (error == null) {
-            throw new DockerClientException("Could not build image");
+        if (imageId != null) {
+            return imageId;
         }
 
-        throw new DockerClientException("Could not build image: " + error);
+        throw new DockerClientException("Could not build image");
     }
 }