Fix frame_id_base argument in camera launch file

[marip8]

This PR updates camera.launch to pass the frame_id_base argument through to nodelet.launch correctly, rather than automatically assigning it to an arbitrary value based on the namespace arguments

[graugans]

Hey @marip8 thanks for your contribution, @desengph will take care of this.

[desengph]

Hi @marip8 we've given your change request a try and think that your suggestions a absolutely valid.
We will include this PR asap.

@graugans can you please merge this.