Use extract_swift_bytes in override_bytes_from_content_type
Use extract_swift_bytes in override_bytes_from_content_type

About half the logic was the same, and it seems better to just implement
that once.

Change-Id: I350da34ef7a3cd0cb74f585f4691992ae64c7eab

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