sleeper_thread: allow interrupting sleep()

This keeps the function consistent with sleep_until() and sleep_for()
which both can be interrupted.
This is relevant to allow an update via a "signal" without an "interval"
in a custom module.

include/util/sleeper_thread.hpp

@@ -61,7 +61,7 @@ class SleeperThread {
   auto sleep() {
     std::unique_lock lk(mutex_);
     CancellationGuard cancel_lock;
-    return condvar_.wait(lk);
+    return condvar_.wait(lk, [this] { return signal_ || !do_run_; });
   }
 
   auto sleep_for(std::chrono::system_clock::duration dur) {