combiners: Handle cases with multiple series and raw keys

The new combiner logic to split out the raw key from ::-delimited series
names breaks down if there is *both* a multiple-generated dataset (from
"duplicates"), *and* a raw key. Fix this by only splitting at the
right-most :: part when trying to find a raw key.

Fixes #166.

Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>

flent/combiners.py

@@ -661,7 +661,7 @@ def get_rawdata(self, resultset, series):
             rawdata = self._get_series(resultset, key, ensure=raw_key)
         except KeyError:
             if '::' in key and 'raw_key' not in series:
-                key, raw_key = key.split("::")
+                key, raw_key = key.rsplit("::", 1)
                 try:
                     rawdata = self._get_series(resultset, key, ensure=raw_key)
                 except KeyError: