Fixes ConfigDrive bug on Windows

Files must be written specifying "wb" instead of "w"
to support binary files on both Windows and Linux.

Closes-Bug: #1261585

(cherry-picked from commit 1fc9eafab43accc127044351106983e2cb215520)

Change-Id: I069845136df4a11b54c931a71575ca3efb9bc6d0