Create create_test_table() function earlier in user guide.
Create create_test_table() function earlier in user guide.

This function (which creates lots of tables) is generally useful for testing (not just stress testing) so create it as soon as the cluster is created.

Also add the data parameter which will insert a single row into the table so the file on disk is not zero bytes.

pgbackrest/pgbackrest,pgbackrest/pgbackrest,pgbackrest/pgbackrest