add debug log line

src/main/java/org/gcube/datatransfer/resolver/services/StorageIDResolver.java

@@ -347,6 +347,7 @@ public class StorageIDResolver {
 				LOG.debug("going to close an old storage-client instance");
 				try {
 					storageManagerClient.forceClose();
+					LOG.debug("storage-client closed");
 				}catch(Exception e) {
 					LOG.warn("Some problem occurred during the close operation:"+e.getMessage()+" Going to open another connection");
 				}