task: start up more worker threads when unpausing

When paused, TaskConsumer threads will eventually notice the paused
condition and exit; however, there's nothing to restart threads when
exiting the paused state.

When unpausing, and while the lock is already held, create TaskConsumer
threads as needed to reach the target thread count.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

lib/task.cc

@@ -645,6 +645,9 @@ namespace crucible {
 		unique_lock<mutex> lock(m_mutex);
 		m_paused = paused;
 		m_condvar.notify_all();
+		if (!m_paused) {
+			start_threads_nolock();
+		}
 		lock.unlock();
 	}