Swarm API /info endpoint has \b chars

[nishanttotla]

This was done to make the output human readable, by adding these extra characters and piggybacking on top of DriverStatus field in the Docker Engine API (here).

The proposal is to add a new field in the Docker Engine API for Swarm to use so that the \b can be removed.

Some relevant discussion on this was previously at #735, #1214, and #1147.

Corresponding issue in docker/docker: moby/moby#19277

cc @vieux