Correct index path validation

Author: benwtrent

qa/vector/src/main/java/org/elasticsearch/test/knn/KnnIndexTester.java

@@ -177,13 +177,8 @@ public static void main(String[] args) throws Exception {
                     cmdLineArgs.vectorSpace(),
                     cmdLineArgs.numDocs()
                 );
-                if (Files.exists(indexPath) == false) {
-                    if (cmdLineArgs.reindex() == false) {
-                        throw new IllegalArgumentException("Index path does not exist: " + indexPath);
-                    }
-                    if (cmdLineArgs.forceMerge()) {
-                        throw new IllegalArgumentException("Force merging without an existing index in: " + indexPath);
-                    }
+                if (cmdLineArgs.reindex() == false && Files.exists(indexPath) == false) {
+                    throw new IllegalArgumentException("Index path does not exist: " + indexPath);
                 }
                 if (cmdLineArgs.reindex()) {
                     knnIndexer.createIndex(result);

qa/vector/src/main/java/org/elasticsearch/test/knn/KnnIndexer.java

@@ -304,7 +304,7 @@ private void readNext() throws IOException {
                 bytes.position(0);
                 // wrap around back to the start of the file if we hit the end:
                 logger.warn("VectorReader hit EOF when reading " + this.input + "; now wrapping around to start of file again");
-                this.input.position(position);
+                input.position(position);
                 bytesRead = Channels.readFromFileChannel(this.input, position, bytes);
                 if (bytesRead < bytes.capacity()) {
                     throw new IllegalStateException(