Avoid to flood the logs with purgeOnDisconnection print

Change-Id: I1c4ec0e2752180642e2e6da7c098fe0a99df756f
diff --git a/app/src/main/java/org/onosproject/segmentrouting/config/DeviceConfiguration.java b/app/src/main/java/org/onosproject/segmentrouting/config/DeviceConfiguration.java
index 5013e83..d161f63 100644
--- a/app/src/main/java/org/onosproject/segmentrouting/config/DeviceConfiguration.java
+++ b/app/src/main/java/org/onosproject/segmentrouting/config/DeviceConfiguration.java
@@ -110,12 +110,14 @@
         Set<DeviceId> deviceSubjects =
                 srManager.cfgService.getSubjects(DeviceId.class, SegmentRoutingDeviceConfig.class);
         deviceSubjects.forEach(subject -> {
-            //Setting purge on disconnection flag for the device SR has control over.
-            // addConfig returns a config if it exists or creates a new one.
-            log.info("PurgeOnDisconnection set to true for device {}", subject);
             BasicDeviceConfig basicDeviceConfig = srManager.cfgService.addConfig(subject, BasicDeviceConfig.class);
-            basicDeviceConfig.purgeOnDisconnection(true);
-            srManager.cfgService.applyConfig(subject, BasicDeviceConfig.class, basicDeviceConfig.node());
+            if (!basicDeviceConfig.purgeOnDisconnection()) {
+                // Setting purge on disconnection flag for the device SR has control over.
+                // addConfig returns a config if it exists or creates a new one.
+                log.info("PurgeOnDisconnection set to true for device {}", subject);
+                basicDeviceConfig.purgeOnDisconnection(true);
+                srManager.cfgService.applyConfig(subject, BasicDeviceConfig.class, basicDeviceConfig.node());
+            }
             SegmentRoutingDeviceConfig config =
                     srManager.cfgService.getConfig(subject, SegmentRoutingDeviceConfig.class);
             SegmentRouterInfo info = new SegmentRouterInfo();