Release PQconninfoOptions array in GetDbnameFromConnectionOptions().
It wasn't getting freed in one code path, which Coverity identified as
a resource leak. It's probably of little consequence, but re-ordering
the code into the correct sequence is no more work than dismissing the
complaint. Minor oversight in commit
a145f424d.
While here, improve the unreasonably clunky coding of
FindDbnameInConnParams: use of an output parameter is unnecessary
and prone to uninitialized-variable problems.