- Move addScripts and addFile from environments/cloudinit.go to cloudinit.Config methods.
- Switch expected to a literla string.
- Go fmt
[r=sidnei] Move addFile, addScripts to cloudinit.Config

Those were buried down into environs/cloudinit.go, and they will be useful
elsewhere for an upcoming branch of mine. Also changed usage of chmod to
'install -m', so the file is created with the correct mode first, and then
written to, which increases security a teensy bit.

https://codereview.appspot.com/12352043/

R=dimitern, natefinch