cloudinit: export AddBootTextFile

This will be needed by the Joyent provider.
provider/joyent: add a static route for the internal network

Fixes LP #1401130.
Merge pull request #1318 from mjs/1401130-joyent-routing-1.21

provider/joyent: add a static route for the internal network

Backport from master. Fixes LP #1401130.

(Review request: http://reviews.vapour.ws/r/637/)