Allow connection to self when impersonator set
    
    If the target of a context establishment is the impersonator itself,
    then allow it. This kind of context establishment is used by tools like
    mod_auth_gssapi to be able to inspect the ticket just obtained via
    impersonation and it is basically a noop as the acceptor and the
    impersonator are the same entitiy.
    
    Signed-off-by: Simo Sorce <simo@redhat.com>
    Reviewed-by: Robbie Harwood <rharwood@redhat.com>
    Merges: #172