Fix destructor of GazeboRosVideo

[davetcoleman]

Fixes #354 with the destructor warning:

terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::lock_error> >'
terminate called recursively
  what():  boost: mutex lock failed in pthread_mutex_lock: Invalid argument
Aborted (core dumped)

This fix was copied from the GazeboRosForce plugin.

I also cleaned up the file while I was at it.

This PR is sponsored by Vicarious

[IanTheEngineer]

Well done, Dave! I not tested your patch yet, but I'd bet that you've just fixed the core-dump issue that I reported ages ago: #354

[IanTheEngineer]

Oops! I see that you've already linked the two tickets :)

[j-rivero]

@osrf-jenkins run test please

[davetcoleman]

For some reason the tests seem stuck

[j-rivero]

run test please

[davetcoleman]

one test passed, the other still seems stuck...

[j-rivero]

one test passed, the other still seems stuck...

Yep, some problems with the integration into the testing farm. I think that we are good to go. Feel free to resolve the conflict and merge

[davetcoleman]

Conflicts fixed, all checks have passed, merging