simplify connection handling in setup script

- factor out runWithEnv
- require explicit connect() call to avoid rechecking for oDB
  (more for readability than for speed)
- clean DSNInfo of empty strings and simplify check for entries

utils/update.php

@@ -110,6 +110,7 @@ if ($aResult['init-updates']) {
                                       'enable-diff-updates' => true,
                                       'verbose' => $aResult['verbose']
                                      ));
+        $cSetup->connect();
         $cSetup->createFunctions();
     }