catch NameNotFoundException to return false as we check a group existence

git-svn-id: https://svn.apache.org/repos/asf/archiva/redback/redback-core/trunk@1433977 13f79535-47bb-0310-9956-ffa450edef68
add unit test for hasRole

git-svn-id: https://svn.apache.org/repos/asf/archiva/redback/redback-core/trunk@1433978 13f79535-47bb-0310-9956-ffa450edef68