Changed default borrow behaviour to simply get current cell definition if a reservation exists already.

Change-Id: I365233a78be6033d176e33c3c3b3ad33f791d85e
diff --git a/utils/warden/src/main/java/org/onlab/warden/WardenServlet.java b/utils/warden/src/main/java/org/onlab/warden/WardenServlet.java
index 9f6ad33..a5f4f29 100644
--- a/utils/warden/src/main/java/org/onlab/warden/WardenServlet.java
+++ b/utils/warden/src/main/java/org/onlab/warden/WardenServlet.java
@@ -70,7 +70,7 @@
             String sshKey = new String(ByteStreams.toByteArray(req.getInputStream()), "UTF-8");
             String userName = req.getParameter("user");
             String sd = req.getParameter("duration");
-            int duration = isNullOrEmpty(sd) ? 60 : Integer.parseInt(sd);
+            int duration = isNullOrEmpty(sd) ? 0 : Integer.parseInt(sd);
             String cellDefinition = warden.borrowCell(userName, sshKey, duration);
             out.println(cellDefinition);
         } catch (Exception e) {