LP1948594: Fix pgtap live test

LP1948594: Fix pgtap live test

Fix the lp1145213_test_func_asset.merge_record_assets.pg pgtap live
test by removing the COMMIT and adding a ROLLBACK at the end.  This
permits the test to run multiple times without requiring a database
reload.

To verify the bug:

1. Install the pgtap package appropriate for your PostgreSQL database
version.

2. Load a fresh database with eg_db_config using the --load-all-sample
option.

3. Create the pgtap extension in the evergreen database.

4. Run the Open-ILS/src/sql/Pg/live_t/ tests with pg_prove.

5. Repeat step 4, and if this patch has not been applied, then the
lp1145213_test_func_asset.merge_record_assets.pg tests will fail on
the second run.

To test the fix, repeat steps 2 - 5, above, after pulling this commit.
Step 5 should succeed.

Signed-off-by: Jason Stephenson <jason@sigio.com>
Signed-off-by: Galen Charlton <gmc@equinoxOLI.org>