@Override
  public String toString() {
    return "[Permission: " + rawExpression() + "]";
  }
Check if two permission equals regardless of actions. It is useful when merging a new
permission with an existed permission which needs to check two permissions's fields.
@param obj instance
@return true if equals, false otherwise
hbase-client/src/main/java/org/apache/hadoop/hbase/security/access/Permission.java