Set murmur3_partitioner_ignore_msb_bits to 12 (enabling the new sharding
algorithm), but do this in scylla.yaml rather than the built-in defaults.
This avoids changing the configuration for existing clusters, as their
scylla.yaml file will not be updated during the upgrade.
Message-Id: <20170214123253.3933-1-avi@scylladb.com>
(cherry picked from commit 9b113ffd3e)