Fix memory leak in the OTP last token plugin
    
    Three memory leaks are addressed:
    
    1. String values retrieved from the pblock need to be manually
    freed.
    
    2. The list of objectclasses retreived from the pblock need to be
    freed.
    
    3. Internal search results need to be freed.
    
    Fixes: https://pagure.io/freeipa/issue/9403
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Rafael Guterres Jeffman <rjeffman@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>