Consider the exit family when applying guard restrictions.

When the new path selection logic went into place, I accidentally
dropped the code that considered the _family_ of the exit node when
deciding if the guard was usable, and we didn't catch that during
code review.

This patch makes the guard_restriction_t code consider the exit
family as well, and adds some (hopefully redundant) checks for the
case where we lack a node_t for a guard but we have a bridge_info_t
for it.

Fixes bug 22753; bugfix on 0.3.0.1-alpha. Tracked as TROVE-2016-006
and CVE-2017-0377.
entry_guard_failed(circuit_guard_state_t **guard_state_p)
{
  if (BUG(*guard_state_p == NULL))
    return;

  entry_guard_t *guard = entry_guard_handle_get((*guard_state_p)->guard);
  if (! guard || BUG(guard->in_selection == NULL))
    return;

  entry_guards_note_guard_failure(guard->in_selection, guard);

  (*guard_state_p)->state = GUARD_CIRC_STATE_DEAD;
  (*guard_state_p)->state_set_at = approx_time();
}

entry_guard_failed(circuit_guard_state_t **guard_state_p)
{
  if (BUG(*guard_state_p == NULL))
    return;

  entry_guard_t *guard = entry_guard_handle_get((*guard_state_p)->guard);
  if (! guard || BUG(guard->in_selection == NULL))
    return;

  entry_guards_note_guard_failure(guard->in_selection, guard);

  (*guard_state_p)->state = GUARD_CIRC_STATE_DEAD;
  (*guard_state_p)->state_set_at = approx_time();
}
