bitbake: data: Don't allow renameVar calls with equivalent keys

While usually a programming error, the behavior can cause a Parser
instance to eventually gobble up a significant amount of memory,
greatly affecting system performance.  Try to avoid getting into
that situation and alert the user about what they attempted to do.

(Bitbake rev: 01bf0912eef5700d61c6e3c9138cb4b6825ee782)

Signed-off-by: Kyle Russell <bkylerussell@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/data_smart.py

@@ -607,6 +607,10 @@ class DataSmart(MutableMapping):
         """
         Rename the variable key to newkey
         """
+        if key == newkey:
+            bb.warn("Calling renameVar with equivalent keys (%s) is invalid" % key)
+            return
+
         if '_remote_data' in self.dict:
             connector = self.dict["_remote_data"]["_content"]
             res = connector.renameVar(key, newkey)