lime-utils: get_node_status, Rewrite the functionality in order to be easier to test.

[germanferrero]

A recent regression affected this functionality. And it was fixed by https://github.com/libremesh/lime-packages/pull/757 Implementing a unit test for it to avoid future regressions is desired, but not straight forward since currently the function has multiple responsibilities. One possible approach would be to split it in two:

• most_active neighbor
• the rest of the "status" And do unit tests for each of it.

[ilario]

@selankon what do you think about this issue? Has it alredy been fixed?