Revert the delete as we go optimization for aggregate and union
Merge pull request #1402 from VoltDB/ENG-6403-valgrind

Revert the delete as we go optimization for aggregate and union
Merge HEAD, branches 'Lu-Weiss-IW' and 'Lu-Weiss-IW' of https://github.com/VoltDB/voltdb into Lu-Weiss-IW
Merge branches 'Lu-Weiss-IW' and 'Lu-Weiss-IW' of https://github.com/VoltDB/voltdb into Lu-Weiss-IW
Fix a issue that piechart not immediately redraw after changing display
metrics.