userportal,webadmin: fix available locale variable

- The available locale variable was not being set properly
  in maven, causing the build to fail when selecting all
  locales. This patch fixes that issues as well as use the
  variable in webadmin/userportal gwt xml.
- Removed hard coded version for maven plugin, now it is being
  managed by a parent pom.

Change-Id: Icc90fdcd05dd460cce4b2084a8e5793b77b5b09b
Signed-off-by: Alexander Wels <awels@redhat.com>