logic: reduced waiting time when interrupting indexer processes

* made multiprocess AST traversal interruptible again
* removed const variables that define sleep times for threads

java_indexer/src/main/java/com/sourcetrail/JavaIndexer.java

@@ -97,6 +97,8 @@ public class JavaIndexer
 				visitor = new ContextAwareAstVisitor(astVisitorClient, path.toFile(), fileContent, cu);
 			}
 			
+			astVisitorClient.logInfo("starting AST traversal");
+			
 			cu.accept(visitor);
 	
 			for (IProblem problem: cu.getProblems())