swarming: Add server-side implementation for supplemental bot_config

appengine/swarming/server/bot_groups_config_test.py

Index: appengine/swarming/server/bot_groups_config_test.py
diff --git a/appengine/swarming/server/bot_groups_config_test.py b/appengine/swarming/server/bot_groups_config_test.py
index 99faf8f0ee0fe32dcf6bddb5ca2622d9042cdb9c..e77b216808620313d671191e5ddeacb1b1c8b31b 100755
--- a/appengine/swarming/server/bot_groups_config_test.py
+++ b/appengine/swarming/server/bot_groups_config_test.py
@@ -46,21 +46,24 @@ EXPECTED_GROUP_1 = bot_groups_config._make_bot_group_config(
     require_service_account=u'',
     ip_whitelist=u'',
     owners=(u'owner@example.com',),
-    dimensions={u'pool': [u'A', u'B'], u'other': [u'D']})
+    dimensions={u'pool': [u'A', u'B'], u'other': [u'D']},
+    bot_config_script='')
 
 EXPECTED_GROUP_2 = bot_groups_config._make_bot_group_config(
     require_luci_machine_token=False,
     require_service_account=u'a@example.com',
     ip_whitelist=u'',
     owners=(),
-    dimensions={u'pool': []})
+    dimensions={u'pool': []},
+    bot_config_script='')
 
 EXPECTED_GROUP_3 = bot_groups_config._make_bot_group_config(
     require_luci_machine_token=False,
     require_service_account=u'',
     ip_whitelist=u'bots',
     owners=(),
-    dimensions={u'pool': [u'default']})
+    dimensions={u'pool': [u'default']},
+    bot_config_script='')
 
 
 DEFAULT_AUTH_CFG = bots_pb2.BotAuth(ip_whitelist='bots')
@@ -84,8 +87,8 @@ class BotGroupsConfigTest(test_case.TestCase):
     utils.clear_cache(bot_groups_config._fetch_bot_groups)
 
   def test_version(self):
-    self.assertEqual('hash:4564ed4cc34544', EXPECTED_GROUP_1.version)
-    self.assertEqual('hash:18206c33fffaa8', EXPECTED_GROUP_2.version)
+    self.assertEqual('hash:ed9cb17d3d6552', EXPECTED_GROUP_1.version)
+    self.assertEqual('hash:73199bbf8cfe47', EXPECTED_GROUP_2.version)
 
   def test_expand_bot_id_expr_success(self):
     def check(expected, expr):