Fix high priority findbugs reported issues

Fixed some code that was reporting findbugs errors

Implemented a suppression mechanism for findbugs
reported errors and a suppression file.

Change-Id: Ie8a2e84cc57ec6ddfa14d782ee89feb095b9dd59
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DistributedLock.java b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DistributedLock.java
index 48a45c4..4998179 100644
--- a/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DistributedLock.java
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/service/impl/DistributedLock.java
@@ -2,6 +2,7 @@
 
 import static org.slf4j.LoggerFactory.getLogger;
 
+import java.nio.charset.StandardCharsets;
 import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
@@ -41,7 +42,9 @@
         this.databaseService = databaseService;
         this.lockManager = lockManager;
         this.lockId =
-                (UUID.randomUUID().toString() + "::" + clusterService.getLocalNode().id().toString()).getBytes();
+                (UUID.randomUUID().toString() + "::" +
+                        clusterService.getLocalNode().id().toString()).
+                        getBytes(StandardCharsets.UTF_8);
     }
 
     @Override