Move all Linux GCE bots to Debian

NOTREECHECKS:true
Bug: skia:
Change-Id: I612989c6ce2f309d2f70f896500f73e4baa971a7
Reviewed-on: https://skia-review.googlesource.com/19811
Commit-Queue: Eric Boren <borenet@google.com>
Reviewed-by: Eric Boren <borenet@google.com>
6 files changed