genpy: improving the run-time dependency

When importing the rosbag module in python, it fails in a genpy python module
complaining about missing the shutil python module. The shutils module is
provided by python-shell.
rosbag: adding run-time dependencies

When importing the rosbag python module, it requires these python modules.
rostopic: adding run-time dependency

The rostopic tool needs the rosbag python module for its execution.
rosbash: adding run-time dependencies

The rosbash tools does not run with the BusyBox shell, and requires
the bash and the common find utility.