Fix for password authentication does not work in certain cases

Fix for password authentication does not work in certain cases

Pgpool-II was only trying to get the password from the pool_passwd file when
backends were configured to use password authentication.  And when the password
is not present in the pool_passwd file it was failing without trying to get the
password from the user even when clear text authentication was allowed on
frontend connections.

The fix is to use clear text password authentication with frontend to get the
user password (If it is allowed by the configuration) when the password for the
connecting user is not found in the pool_passwd file.

The issue was reported by "Tatsuo Ishii<ishii@sraoss.co.jp>"