Some code cleanup:
* Use a field for setting EC2 metadata instead of env-vars in testing;
but keep environment variables for backward compatibility reasons
* Update tests to use testify
This removes a cyclical dependency when importing client/structs from
dependencies of the plugin_loader, specifically, drivers. Due to
client/config also depending on the plugin_loader.
It also better reflects the ownership of fingerprint structs, as they
are fairly internal to the fingerprint manager.
Certain environments use WARN for serious logging; however, it's very
possible to have machines without some of the fingerprinted keys
(public-ipv4 and public-hostname specifcally). Setting log level to
INFO seems more consistent with this possibility.
This PR:
* Makes AWS network speeds more granular
* Makes `network_speed` an override and not a default
* Adds a default of 1000 MBits if no network link speed is detected.
Fixes#1985
Fix URL. It was printing an error message on startup:
```
2015/11/13 15:49:21 [ERR] fingerprint.env_aws: Error querying AWS Metadata URL, skipping
```
By the way is it safe to use latest? Is there a chance that Amazon decides to change the format of the metadata? It could be safer to use something like `http://169.254.169.254/2014-11-05/meta-data`
GCE and AWS both expose metadata servers, and GCE's 404 response
includes the URL in the content, which maatches the regex. So,
check the response code as well and if a 4xx code comes back,
take that to meanit's not AWS.
