Remove the root url parameter for -from-metadata-service since this
is a guarenteed value. Additionally, check for both ec2 and openstack
urls for the metadata and userdata. Fix a bug with the -from-url
option and a panic on an empty response.
Move the old metadata-service datasource to url datasource. This new datasource
checks for the existance of meta-data.json and if it doesn't exist, walks the
meta-data directory to build a metadata blob.
Supports retries with exponential backoff as well as connection
timeouts and the ability to skip SSL/TLS verification.
This commit also refactors datasource and initialize packages
in order to use the new HTTP client.
