Get node's logger name from rcl

[dhood]

connects to ros2/rcl#212

I have a question on this PR. Which approach is more appropriate in the context of node interfaces:

1. logging interface directly calling through to rcl using the node handle (this commit), or
2. going through node_base (this commit)?

It's not clear to me since on one hand the logger name is used (only) by the logging interface, but on the other hand at the rcl level it is tightly coupled to what seems to be the node "base".

[dirk-thomas]

I am leaning towards the first option since imo the second one keeps adding more and more API to the node / interfaces (which I am not a big fan of). But I don't mind either way and would let others comment on this which are more familiar with the pros / cons of the two options.

[wjwwood]

Option 3?

Provide the get_logger_name() function on the NodeLoggingInterface and "dog food" it (if possible, essential option 1 if not possible) in the NodeLogging implementation, so that if it is used from outside, it can be mocked via the NodeLoggingInterface pure virtual base class.

[dhood]

waiting for review @ros2/team

[Karsten1987]

this looks good to me. You may want to have an approval from @dirk-thomas or @wjwwood though.