BUG: Fix bar data contains check when override is used.

The override should be used to filter out symbols not in the universe,
however it was returning false positives.

To remove the false positives, after the contains check passes,
ensure that the key exists in the _data member.

zipline/protocol.py

@@ -140,7 +140,10 @@ class BarData(object):
 
     def __contains__(self, name):
         if self._contains_override:
-            return self._contains_override(name)
+            if self._contains_override(name):
+                return name in self._data
+            else:
+                return False
         else:
             return name in self._data