pkg/query: Correctly sum up total cumulative value

[metalmatze]

We were counting inlined functions additionally.

[brancz]

I guess as long as this is consistent with our previous flamegraph implementation I'm happy with it, but I'll be honest I don't understand this change.

[metalmatze]

It is now.
The real root cause is folded away by GitHub, it's the lines above:

for k := len(location.Lines) - 1; k >= 0; k-- {
	line := location.Lines[k]

We were adding the cumulative value multiple times if the leaf is an inlined function.