Add a test to cover Distributor pruning feature

To test if distributor can prune, we add an event to storage and
then delete the waiting task from storage to simulate it being
started by another node. We then assert that the project task
gets pruned from the work queue by the time the next distribution
cycle completes.

Change-Id: Ifeed8444986be03bddf443fed94170c8ee5ae72c

src/test/java/com/googlesource/gerrit/plugins/replication/ReplicationDistributorIT.java

diff --git a/src/test/java/com/googlesource/gerrit/plugins/replication/ReplicationDistributorIT.java b/src/test/java/com/googlesource/gerrit/plugins/replication/ReplicationDistributorIT.java
index 5674732..5ade68d 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/replication/ReplicationDistributorIT.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/replication/ReplicationDistributorIT.java
@@ -82,6 +82,21 @@
     }
   }
 
+  @Test
+  public void distributorPrunesTaskFromWorkQueue() throws Exception {
+    createTestProject(project + "replica");
+    setReplicationDestination("foo", "replica", ALL_PROJECTS, Integer.MAX_VALUE);
+    reloadConfig();
+
+    String newBranch = "refs/heads/foo_branch";
+    createBranch(project, "refs/heads/master", newBranch);
+
+    deleteWaitingReplicationTasks(newBranch); // This simulates the work being started by other node
+
+    assertThat(waitForProjectTaskCount(0, Duration.ofSeconds(TEST_DISTRIBUTION_CYCLE_SECONDS)))
+        .isTrue();
+  }
+
   private List<WorkQueue.Task<?>> getProjectTasks() {
     return getInstance(WorkQueue.class).getTasks().stream()
         .filter(t -> t instanceof WorkQueue.ProjectTask)