Don't return multiple elements for grain 'osmajorrelease'.

Before this fix, the output of the 'osmajorrelease' grain looked like
this:

    osmajorrelease:
        7
        0.1406

Now it'll only return the actual major release number:

    osmajorrelease: 7

This fix needs to be merged into `develop` and cherry-picked into `2014.1`.