Mark x86-alex as the release master.

x86-alex is the release master on the waterfall so it needs to be marked
as such in the config.

BUG=none
TEST=unit test

Change-Id: Ibd9a44e9267a03e9d02369170e7d03d913dc71b2
Reviewed-on: https://chromium-review.googlesource.com/199623
Reviewed-by: Dharani Govindan <dharani@chromium.org>
Tested-by: Dharani Govindan <dharani@chromium.org>
diff --git a/buildbot/cbuildbot_config.py b/buildbot/cbuildbot_config.py
index 35b8b84..9bef3a8 100755
--- a/buildbot/cbuildbot_config.py
+++ b/buildbot/cbuildbot_config.py
@@ -1835,7 +1835,6 @@
 
 _release.add_config('x86-mario-release',
   boards=['x86-mario'],
-  master=True,
 )
 
 ### Release config groups.
@@ -1843,6 +1842,7 @@
 _config.add_group('x86-alex-release-group',
   _release.add_config('x86-alex-release',
     boards=['x86-alex'],
+    master=True,
   ),
   _grouped_variant_release.add_config('x86-alex_he-release',
     boards=['x86-alex_he'],