Put snooze() back because timing issues on my machine actually showed that the

two calls where actually necessary to guaranteed get an unused revid between
two used ones.

src/ZODB/tests/RevisionStorage.py

@@ -49,6 +49,8 @@ class RevisionStorage:
             # guarantees that the next timestamp will be at least one
             # larger (and probably much more than that) than the previous
             # one.
+            snooze()
+            snooze()
             revid = self._dostore(oid, revid, data=MinPO(i))
             revs.append(self._storage.load(oid, ""))