pw_transfer: Prevent zero length sleeps on the transfer thread

The transfer thread was ignoring the next timeout and always setting
sleepFor to 0.

Fixes: b/236881052
Change-Id: Ic08fd9195f4cb7a315bb791220c99d7c677496cb
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/99680
Reviewed-by: Alexei Frolov <frolv@google.com>
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>

pw_transfer/java/main/dev/pigweed/pw_transfer/TransferEventHandler.java

@@ -179,7 +179,7 @@ private void enqueueEvent(Event event) {
   }
 
   private void handleNextEvent() {
-    final long sleepFor = Math.min(0, Instant.now().until(getNextTimeout(), TIME_UNIT));
+    final long sleepFor = TIME_UNIT.between(Instant.now(), getNextTimeout());
     try {
       Event event = events.poll(sleepFor, POLL_TIME_UNIT);
       if (event != null) {