[rosbag] Fix waitForSubscribers hanging with simtime (ros#1543)

* [rosbag] Fix waitForSubscribers hanging with simtime

Use Walltime for sleep as clock is not running yet

* Simplify wallsleep in waitForSubscribers

Co-Authored-By: AlexReimann <alexander.reimann@enway.ai>

tools/rosbag/src/player.cpp

@@ -452,7 +452,7 @@ void Player::waitForSubscribers() const
         foreach(const PublisherMap::value_type& pub, publishers_) {
             all_topics_subscribed &= pub.second.getNumSubscribers() > 0;
         }
-        ros::Duration(0.1).sleep();
+        ros::WallDuration(0.1).sleep();
     }
     std::cout << "Finished waiting for subscribers." << std::endl;
 }