Fix timestamp inversion bug (#1144)

* Fix timestamp inversion bug

Set the number of commitLog buckets to 1 in CommitLog replay tests to
expose all timestamp inversion problems due to replay. Fixed
PollAckFlowTest which is related to this problem.

Also fixed a few tests that failed to advance the fake clock when they
should, using the following approaches:

- If DatabaseHelper used but clock is not injected, do it. This
  allows us to remove some unnecessary manual clock advances.
- Manually advance the clock where convenient.
- Enable clock autoIncrement mode when calling production classes that
  performs multiple transactions.

We should consider making 1-bucket the default setting for tests. This
is left to another PR.

common/src/testing/java/google/registry/testing/FakeClock.java

@@ -22,6 +22,7 @@ import google.registry.util.Clock;
 import java.util.concurrent.atomic.AtomicLong;
 import javax.annotation.concurrent.ThreadSafe;
 import org.joda.time.DateTime;
+import org.joda.time.Duration;
 import org.joda.time.ReadableDuration;
 import org.joda.time.ReadableInstant;
 
@@ -81,4 +82,14 @@ public final class FakeClock implements Clock {
   public void setTo(ReadableInstant time) {
     currentTimeMillis.set(time.getMillis());
   }
+
+  /** Invokes {@link #setAutoIncrementStep} with one millisecond-step. */
+  public FakeClock setAutoIncrementByOneMilli() {
+    return setAutoIncrementStep(Duration.millis(1));
+  }
+
+  /** Disables the auto-increment mode. */
+  public FakeClock disableAutoIncrement() {
+    return setAutoIncrementStep(Duration.ZERO);
+  }
 }