Add current stable maven-war-plugin

Jenkins tries to use old version 2.1.1 but this artifact is not
available anymore.

pom.xml

@@ -495,6 +495,11 @@
 				<artifactId>groovy-maven-plugin</artifactId>
 				<version>1.4</version>
 			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-war-plugin</artifactId>
+				<version>2.3</version>
+			</plugin>
 		</plugins>
 	</build>