Test EC chunk_transformer with larger input chunks
Test EC chunk_transformer with larger input chunks

The tests were lacking coverage for the chunk_transformer
reading multiple segment_size pieces from an input chunk.
This patch modifies test_chunk_transformer to exercise more
input chunk scenarios.

Also improve variable naming and comments in
_test_determine_chunk_destinations_prioritize

Change-Id: I4eb55ee3e87dae478828f7ccba86fec267492bd8
Related-Change: Ib9e8a6f67c2985164dd20b049c7f144f19fd1822

clayg/swift,psachin/swift,clayg/swift,nadeemsyed/swift,openstack/swift,notmyname/swift,notmyname/swift,swiftstack/swift,psachin/swift,tipabu/swift,clayg/swift,notmyname/swift,smerritt/swift,matthewoliver/swift,redbo/swift,psachin/swift,tipabu/swift,swiftstack/swift,matthewoliver/swift,matthewoliver/swift,clayg/swift,nadeemsyed/swift,notmyname/swift,openstack/swift,tipabu/swift,tipabu/swift,openstack/swift,openstack/swift,smerritt/swift,swiftstack/swift,psachin/swift,smerritt/swift,nadeemsyed/swift,redbo/swift,smerritt/swift,nadeemsyed/swift,matthewoliver/swift