findAnnotations: don't lowercase ids (fixes #2916)

Without this fix, a condition like:

     {key: 'id', operator: '==', value: 'A/B'}

gets mapped to:

     public_id__exact=('A/B'.lower())

which is wrong.

I introduced this bug in b3df5b8. I didn't catch it because I was
mostly interested in the 'layer' key -- but layer names are
conventionally lowercase anyway so lowercasing them had no effect.

pandora/annotation/managers.py

@@ -92,7 +92,7 @@ def parseCondition(condition, user):
     key = str(key)
     if isinstance(v, unicode):
         v = unicodedata.normalize('NFKD', v)
-        if v not in case_sensitive_keys:
+        if k not in case_sensitive_keys:
             v = v.lower()
     if exclude:
         q = ~Q(**{key: v})