Trailing slash (/) on cluster resource causes incorrect authorization logic flow

Trailing slash on cluster resource causes incorrect authorization logic flow. It is debatable whether Ambari should allow this, but since it seems to in other cases - like if the user was an Ambari Administrator - this should be fixed.

The problem occurs in the org.apache.ambari.server.security.authorization.AmbariAuthorizationFilter where the filter attempts to figure out what the user is trying to get access to. Since the regular expression for Cluster resources does acknowledge that a trailing "/" after the cluster name indicates a cluster, the request does not fall through to the Cluster resource handler (org.apache.ambari.server.controller.internal.ClusterResourceProvider) for authorization checks. It uses the legacy logic, which is a little flawed as well.

The fix for this is to allow the trailing "/" in the regular expression representing Cluster requests:

  private static final String API_CLUSTERS_PATTERN = API_VERSION_PREFIX + "/clusters/(\\w+)?";

  private static final String API_CLUSTERS_PATTERN = API_VERSION_PREFIX + "/clusters/(\\w+/?)?";