Using '0' instead of '-' in overview page.

When there is no data in the project, Usage Summary in overview page
always show '-' for `Active Instances` and other values, it would be
better showing '0' instead '-'.

Change-Id: I121de36ac9dc5ced2218c08b82a8b2e4a3d5e459
Closes-bug: 1288015
Merge "Using '0' instead of '-' in overview page."