G1RegionsSmallerThanCommitSizeMapper::commit_regions() calculate all_zero_filled wrong for callback

In G1RegionsSmallerThanCommitSizeMapper::commit_regions() there is a callback used to notify the owner when memory is commited. This callback includes a boolean telling if the committed memory was zero or not, but in the current implementation this value is not always correct.

The value is set to false if any region committed belongs to an already committed page, this becomes a problem when we commit multiple regions belonging to the same page. Even if the page was just committed (and therefore zero) we will update the value to false when committing the second region belonging to the same.