Revert latch removal, as this somehow broke the tests

src/main/java/de/tum/in/www1/artemis/service/connectors/localci/buildagent/BuildJobContainerService.java

@@ -13,6 +13,7 @@
 import java.nio.file.Paths;
 import java.time.ZonedDateTime;
 import java.util.*;
+import java.util.concurrent.CountDownLatch;
 
 import org.apache.commons.compress.archivers.tar.TarArchiveEntry;
 import org.apache.commons.compress.archivers.tar.TarArchiveInputStream;
@@ -322,6 +323,7 @@ private void executeDockerCommand(String containerId, String buildJobId, boolean
             execCreateCmd = execCreateCmd.withUser("root");
         }
         ExecCreateCmdResponse execCreateCmdResponse = execCreateCmd.exec();
+        final CountDownLatch latch = new CountDownLatch(1);
         try {
             dockerClient.execStartCmd(execCreateCmdResponse.getId()).withDetach(detach).exec(new ResultCallback.Adapter<>() {
 
@@ -333,11 +335,20 @@ public void onNext(Frame item) {
                         buildLogsMap.appendBuildLogEntry(buildJobId, buildLogEntry);
                     }
                 }
-            }).awaitCompletion();
+
+                @Override
+                public void onComplete() {
+                    latch.countDown();
+                }
+            });
         }
         catch (ConflictException e) {
             throw new LocalCIException("Could not execute Docker command: " + String.join(" ", command), e);
         }
+
+        try {
+            latch.await();
+        }
         catch (InterruptedException e) {
             throw new LocalCIException("Interrupted while executing Docker command: " + String.join(" ", command), e);
         }