Fix remaining import

Author: jburel

src/main/java/omero/gateway/Gateway.java

@@ -41,7 +41,7 @@
 import java.util.concurrent.TimeUnit;
 
 import org.apache.commons.collections.CollectionUtils;
-import org.apache.commons.lang.StringUtils;
+import org.apache.commons.lang3.StringUtils;
 
 import ome.formats.OMEROMetadataStoreClient;
 import omero.RType;