Accept configdrive info as {path: base64_content} style

[jimrollenhagen]

Discussed with Chris in IRC this morning and decided this was the best way to go.

This also hardcodes the location on disk to write the configdrive to. I don't think that needs to be parameterized.

[comstud]

not necessarily json data anymore, but :)

[russellhaering]

Yeah, I think this is fine, +1

[russellhaering]

@pquerna thoughts on this? We had some back-and-forth last week, and I saw you mention this on IRC over the weekend.

1. I believe that the teeth-overlord API should resemble Nova's, in that it should allow a user to inject files onto the host filesystem, but shouldn't expose them to the details of configdrive/cloud-init/whatever-else-might-appear-in-the-future.
2. Between the overlord and the agent I'm less opinionated about the API. One option (implemented here) is that the agent is relatively "dumb" and the overlord gives it files to put into configdrive. Another option would be for this to more closely resemble the public API - taking some files and some metadata, and generating the appropriate configdrive layout itself.

I hate base64 as an API as much as the next person, but given that this isn't user-facing, and that we're going to be taking some base64 blobs, I'm alright with this.

[russellhaering]

Is this function actually used outside of tests?

[russellhaering]

I think this prefix (and maybe the one above) should default to openstack. I don't see writing to a teeth prefix being practical in the near future.

[russellhaering]

Other than the "teeth" prefix, LGTM.