UrlResponse: biggest change... make readurl return bytes, making user
know what to do with it.
util: add load_tfile_or_url for loading text file or url
as read_file_or_url now returns bytes
ec2_utils: all meta-data is text, remove non-obvious string translations
DigitalOcean: adjust for ec2_utils
DataSourceGCE, DataSourceMAAS: user-data is binary other fields are text.
openstack.py: read paths without decoding to text. This is ok as paths
other than user-data are json, and load_json will handle
load_file still returns text, and that is what most things use.
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