python: Better check for keys in dicts

python: Better check for keys in dicts

Python 3 lost the dict.has_key() method. Instead it requires using the
"in" operator.

This is also compatible with Python 2.

Signed-off-by: Mathieu Bridon <bochecha@daitauha.fr>
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>