fix tests on new versions of postgres

Fix test suite to run on both postgres >= 9.2 and postgres <= 9.2.

In 9.2 the postgres team changed some names of some columns in the pg_activity_stat table.  This table is used by some tests to look up current queries and connections and forcibly terminate them to simulate disconnects & query errors.  Since the columns changed names these tests broke.

It sucks to have to do "if this version run this query or if that version run that query" but that's the best fix I could come up with.

this closes #261