database/sql.Rows.Next() makes sure to call Close only after exhausting
result rows which would NOT happen when returning early from a bad Scan.
Close being idempotent makes it a great candidate to get always deferred
regardless of what happens later on the result set.
This change also makes sure call Err() after exhausting Next() and
propagate non-nil results from it as the documentation advises.
Closes#764
Signed-off-by: Kiril Vladimiroff <kiril@vladimiroff.org>
* Fall back to postgres when parsing the database connection string for a URI schema fails
* Fix behaviour so that it really tries postgres when URL parsing fails and it complains about unknown schema if it succeeds
