Fix linter error for type comparison

[nsmith-]

In the code we use a lot of type(x) == y conditionals, e.g.

HiggsAnalysis-CombinedLimit/python/DatacardParser.py

Lines 450 to 451 in cc6baaf

	if ret.obs != [] and type(ret.obs) == list: # still as list, must change into map with bin names
	ret.obs = dict([(b, ret.obs[i]) for i, b in enumerate(ret.bins)])

which recently started being checked by flake8, e.g.

./python/DatacardParser.py:450:38: E721 do not compare types, for exact checks use `is` / `is not`, for instance checks use `isinstance()`

A few quick changes, e.g. to isinstance(x, y) would suppress these. For now I've silenced the warning in #856