increase per-channel capacity

* 100 is the default capacity for a channel. If the client doesn't read
the socket fast enough, websocket messages can and will be lost. This
increases the default to 10,000

installer/roles/local_docker/templates/credentials.py.j2

@@ -16,7 +16,10 @@ BROKER_URL = 'redis://{}:{}/'.format(
 
 CHANNEL_LAYERS = {
     'default': {'BACKEND': 'channels_redis.core.RedisChannelLayer',
-                'CONFIG': {'hosts': [("{{ redis_hostname }}", {{ redis_port|int }})]}}
+                'CONFIG': {
+                    'hosts': [("{{ redis_hostname }}", {{ redis_port|int }})],
+                    'capacity': 10000,
+                 }}
 }
 
 CACHES = {