Correctly set test URL in server device driver

Also, the parent DefaultRestSBDevice had a faulty testUrl toString.

Change-Id: I15d9432402aa00d453c3b09cbf5e5c05e82549eb
Signed-off-by: Georgios Katsikas <katsikas.gp@gmail.com>
diff --git a/drivers/server/src/main/java/org/onosproject/drivers/server/ServerDevicesDiscovery.java b/drivers/server/src/main/java/org/onosproject/drivers/server/ServerDevicesDiscovery.java
index ca4e809..b4440e8 100644
--- a/drivers/server/src/main/java/org/onosproject/drivers/server/ServerDevicesDiscovery.java
+++ b/drivers/server/src/main/java/org/onosproject/drivers/server/ServerDevicesDiscovery.java
@@ -352,7 +352,7 @@
         RestServerSBDevice dev = new DefaultRestServerSBDevice(
             device.ip(), device.port(), device.username(),
             device.password(), device.protocol(), device.url(),
-            device.isActive(), device.testUrl().toString(),
+            device.isActive(), device.testUrl().orElse(""),
             vendor, hw, sw, AuthenticationScheme.BASIC, "",
             cpuSet, nicSet
         );
diff --git a/drivers/server/src/main/java/org/onosproject/drivers/server/impl/devices/DefaultRestServerSBDevice.java b/drivers/server/src/main/java/org/onosproject/drivers/server/impl/devices/DefaultRestServerSBDevice.java
index cc2e541..b43c2ec 100644
--- a/drivers/server/src/main/java/org/onosproject/drivers/server/impl/devices/DefaultRestServerSBDevice.java
+++ b/drivers/server/src/main/java/org/onosproject/drivers/server/impl/devices/DefaultRestServerSBDevice.java
@@ -126,11 +126,11 @@
         return MoreObjects.toStringHelper(this)
                 .omitNullValues()
                 .add("url", url())
-                .add("testUrl", testUrl())
                 .add("protocol", protocol())
                 .add("username", username())
-                .add("port", port())
                 .add("ip", ip())
+                .add("port", port())
+                .add("testUrl", testUrl().orElse(null))
                 .add("manufacturer", manufacturer().orElse(null))
                 .add("hwVersion", hwVersion().orElse(null))
                 .add("swVersion", swVersion().orElse(null))