refs #4550 Bugs fixed

print-server.js

@@ -88,7 +88,7 @@ class PrintServer {
             await conn.beginTransaction();
             [[printJob]] = await conn.query(selectQuery);
             if (!printJob) {
-                conn.rollback();
+                await conn.rollback();
                 return;
             }
 
@@ -97,7 +97,7 @@ class PrintServer {
             await conn.query(updateQuery, ['printing', null, jobId]);
             await conn.commit();
         } catch (err) {
-            conn.rollback();
+            await conn.rollback();
             throw err;
         }