Enable Goma fallback by default.

Add a job that doesn't allow fallback so we know when things aren't
working as expected.

Change-Id: If993976d6807635bde455c2091f8a1ba18c41e27
Reviewed-on: https://skia-review.googlesource.com/83700
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Ben Wagner <benjaminwagner@google.com>
7 files changed