In the hardware_interface, some members should be atomic

[AndyZe]

It seems like robot_program_running_ and controller_reset_necessary_ should be std::atomic type for thread safety. I say this because it looks like there is potential to read the variables at the same time as writing them from a callback.

Maybe others as well, like position_controller_running_ and velocity_controller_running_

[fmauch]

Thanks for bringing this up. We will definitely look into this!

[fmauch]

@stefanscherzinger assigning this to me so it pops up in my task list. If you'd like to look into this before me, please let me know.