Fix display of writing nodes from older Pgs
Fix display of writing nodes from older Pgs

Older Pgs (9.0 for example) didn't show table name for
insert/update/delete. Fix template not to assume "scan_on" is available
for writing nodes.

depesz/explain.depesz.com,depesz/explain.depesz.com,depesz/explain.depesz.com,depesz/explain.depesz.com