Do not use persistent pdo connections

At least for blast requests reuse of connections does not work properly.
Instead a lot of open connections remain leading to "Too many clients already"
Fix #57

src/web/includes/TranscriptDB/db.php

@@ -34,7 +34,7 @@ function get_db_connection($connstr, $username, $password) {
             $db = new \LoggedPDO\PDO($connstr, $username, $password, null, $logger);
             //$db->log_replace_params = false;
         } else {
-            $db = new PDO($connstr, $username, $password, array(PDO::ATTR_PERSISTENT => true, PDO::ATTR_EMULATE_PREPARES => false));
+            $db = new PDO($connstr, $username, $password, array(PDO::ATTR_PERSISTENT => false, PDO::ATTR_EMULATE_PREPARES => false));
         }
         #usually stop execution on DB error
         $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);