Prevent re-entering value-set-table.updateContents_.
Prevent re-entering value-set-table.updateContents_.

Setting groupby-picker's currentGroups in updateGroups_ may cause the picker to
fire its event, which causes value-set-table to call updateContents_, then
|set values| proceeds to call updateContents_.
There may be a similar loop possible with show_all.

This isn't causing any visible bad behavior, it just wastes CPU by computing the
same things over and over.

Review-Url: https://codereview.chromium.org/2320103003

benschmaus/catapult,benschmaus/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,sahiljain/catapult,catapult-project/catapult-csm,sahiljain/catapult,catapult-project/catapult,catapult-project/catapult,benschmaus/catapult,catapult-project/catapult-csm,catapult-project/catapult,benschmaus/catapult,catapult-project/catapult,catapult-project/catapult,benschmaus/catapult,sahiljain/catapult,catapult-project/catapult-csm,benschmaus/catapult,sahiljain/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,benschmaus/catapult,sahiljain/catapult,sahiljain/catapult,catapult-project/catapult,catapult-project/catapult