[LTP] [PATCH v2] travis: Use centos:7 instead of centos:6

[Petr Vorel]

Hi,

> Hi!
> > Does have anything block this patch? Or, we should listen some advise 
> > from Jan and Cyril?

> I would be for dropping centos 6 (if nobody objects) after next release,
> which will happen in a couple of weeks anyways.

> So for now on I would be for adding centos 7, so that the next release
> compiles cleanly both on centos 6 and 7.

> Then we can work on our minimal requirements and drop obsolete code.
Make sense. So I merged the original patch.

Kind regards,
Petr