kcc/graph: add __hash__ to InternalEdge for py3

In py3, if a class defines `__eq__()` but not `__hash__()`, its instances will
not be usable as items in hashable collections, e.g.: set.

Add `__hash__()` to InternalEdge, so it can be added to a set in py3.

Signed-off-by: Joe Guo <joeg@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>

python/samba/kcc/graph.py

@@ -805,6 +805,11 @@ class InternalEdge(object):
         self.e_type = eType
         self.site_link = site_link
 
+    def __hash__(self):
+        return hash((
+            self.v1, self.v2, self.red_red, self.repl_info, self.e_type,
+            self.site_link))
+
     def __eq__(self, other):
         return not self < other and not other < self