Fix memcached configuration in local Docker installs

Related: https://github.com/ansible/awx/issues/3719
Signed-off-by: Shane McDonald <me@shanemcd.com>

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

@@ -5,15 +5,16 @@ DATABASES = {
         'NAME': "{{ pg_database }}",
         'USER': "{{ pg_username }}",
         'PASSWORD': "{{ pg_password }}",
-        'HOST': "{{ pg_hostname|default('postgres') }}",
+        'HOST': "{{ pg_hostname | default('postgres') }}",
         'PORT': "{{ pg_port }}",
     }
 }
+
 BROKER_URL = 'amqp://{}:{}@{}:{}/{}'.format(
     "{{ rabbitmq_user }}",
     "{{ rabbitmq_password }}",
-    "rabbitmq",
-    "5672",
+    "{{ rabbitmq_host }}",
+    "{{ rabbitmq_port }}",
     "awx")
 
 CHANNEL_LAYERS = {
@@ -21,3 +22,13 @@ CHANNEL_LAYERS = {
                 'ROUTING': 'awx.main.routing.channel_routing',
                 'CONFIG': {'url': BROKER_URL}}
 }
+
+CACHES = {
+    'default': {
+        'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache',
+        'LOCATION': '{}:{}'.format("{{ memcached_host }}", "{{ memcached_port }}")
+    },
+    'ephemeral': {
+        'BACKEND': 'django.core.cache.backends.locmem.LocMemCache',
+    },
+}