Set @java_xmx for Wildfly

Zanata can sometimes run into a "GC overhead limit exceeded" error
when running with the default 512m of RAM for the -Xmx JAVA_OPTS
variable.

Fortunately the Wildfly module we use has this as a variable for
it, using that (see manifests/install.pp for in the biemond-wildfly
module and associated standalone template for details).

Change-Id: I5d1f03c9d5cd57bb6bbf6650292173a3325cec4d

manifests/wildfly.pp

@@ -28,6 +28,7 @@ class zanata::wildfly(
     install_source => $wildfly_install_source,
     config         => 'standalone.xml',
     java_home      => '/usr/lib/jvm/java-7-openjdk-amd64/jre/',
+    java_xmx       => '2048m',
     require        => Package['openjdk-7-jre-headless'],
   }
 }