Fix dashboard graphite URLs

Fix dashboard graphite URLs

The update to openstack graphite data is now storing nulls instead
of high frequency zero values. Therefore, make the following changes:

1. use stats_counts instead of stats data, as this accesses the raw
counters
2. apply transformNull to all data series so that null -> 0 is handled
correctly
3. add a global drawNullAsZero=true to handle discontinuities

Thanks to jeblair and sdague for tracking this down

Change-Id: Idebc046d7d867d80e2afe1c4b86c526f9205d3d5
Signed-off-by: Ryan Moats <rmoats@us.ibm.com>