note in upgrade guide regarding webapp context changed

git-svn-id: https://svn.apache.org/repos/asf/archiva/trunk@1565995 13f79535-47bb-0310-9956-ffa450edef68
fix link

git-svn-id: https://svn.apache.org/repos/asf/archiva/trunk@1565996 13f79535-47bb-0310-9956-ffa450edef68