[beta6] Dashboards do not save GROUP BY tags

[rkuchan]

My GROUP BY tag clause isn't saved when I create a graph, GROUP BY tags, and save that graph.

Repro steps

Step 1: Create a cool graph and GROUP BY tags

Step 2: Save the graph by clicking on the checkmark

Step 3: See a single series (not three series) in the graph on the dashboard

Step 4: Edit the graph and see that the tags are missing from the query

Step 5: Contemplate life