moblab: Create moblab_quick suite for the CQ.

Created a moblab_quick suite to run the dummy_server suite. This
will be the basic CQ test for moblab.

Updated the stable_cros_version in the global_config.ini to builds
that have the dummy_server suite built in.

BUG=chromium:461966
TEST=trybot build with local test run.

Change-Id: I8c78c3a653bad848ebef0ddeba03f53aec1ab2ca
Reviewed-on: https://chromium-review.googlesource.com/255541
Reviewed-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Simran Basi <sbasi@chromium.org>
Commit-Queue: Simran Basi <sbasi@chromium.org>
Tested-by: Simran Basi <sbasi@chromium.org>
diff --git a/global_config.ini b/global_config.ini
index 78d99c1..5c412c9 100644
--- a/global_config.ini
+++ b/global_config.ini
@@ -205,7 +205,7 @@
 # Use `cli/atest stable_version` command to view or manage stable versions.
 # WARNING! Edit following setting will NOT work if stable versions are stored
 # in afe_stable_versions table already!
-stable_cros_version: R41-6592.0.0
+stable_cros_version: R42-6784.0.0
 stable_build_pattern: %s-release/%s
 source_tree: /usr/local/google/chromeos
 gs_offloading_enabled: True