Fix: querying rollup data does not show aggregated points corresponding to points in ROB

[zlin179]

Fix for issue #1485

Describe your changes
The rollup aggregators only get the points once they leave the ROB.
This PR fixs aggregator so when being queried it will return the current value (considering points in ROB) but will not actually consume the points in ROB.

Testing performed

• Add some unit tests for it and pass it.
• Integrate test by comparing raw data and rollup data queried at the same time

[Dieterbe]

I have started reviewing this. It looks promising, but I suggest in the future to create a cleaner commit history (e.g. by using git rebase -i. E.g. the first commit which claims to just introduce a test, also changes core functionality and does very strange changes to mdata/aggmetrics.go such as removing unrelated code.

I will go ahead and review it in its current shape and will probably squash merge this instead of a regular merge.