Replace proc.cpu.user_p with proc.cpu.total_p

[monicasarbu]

Fixes #631

[andrewkroh]

Since we have the data available to truly calculate proc.cpu.user_p I think we should calculate it so that Topbeat has both proc.cpu.user_p and proc.cpu.total_p. Then there would be no perceived loss of functional nor backwards compatibility issues with dashboards.

[andrewkroh]

The changes made LGTM.

[monicasarbu]

@andrewkroh Yes, indeed we can export both proc.cpu.user_p and proc.cpu.total_p, but I would prefer to have only one to be similar with what top command displays. One reason is that I am afraid that people will get confuse if topbeat exports two percentages and the top command shows only one. Another reason is that I prefer to keep the data that we export to the minimum. To fix the second concern, we could add another config option that decides when to export proc.cpu.user_p ... What are your thoughts?

[andrewkroh]

Ok. I don't think I would bother with the config option. As long as we document the breaking change to the schema, users should be able to update any custom dashboards.

[dedemorton]

@monicasarbu The screen captures in the getting started doc also need to be updated to reflect the name change: https://www.elastic.co/guide/en/beats/topbeat/current/topbeat-getting-started.html.

Should I open a doc issue to remind me to do this, or do you want to do a quick screen grab and add it yourself? I'm not sure my data will be as interesting as your data. :-)