Always set ALLOWED_HOSTS=['*'] for horizon

If devstack is deployed in the VM with defined
public IP address (like 192.168.10.6) it is not possible to
access the Horizon from the browser.
This is because DEBUG=True means that ALLOWED_HOSTS, if not set,
is equal to ['localhost', '127.0.0.1', '[::1]'] according
to Django's documentation.

Change-Id: I0ab2b57e459dbfa3b01b3e9388bbcefac076a142
Co-Authored-By: David Lyle <dklyle0@gmail.com>
Closes-Bug: #1643050
diff --git a/lib/horizon b/lib/horizon
index 78cbe8b..f5e9c7e 100644
--- a/lib/horizon
+++ b/lib/horizon
@@ -97,6 +97,11 @@
     _horizon_config_set $local_settings "" OPENSTACK_API_VERSIONS {\"identity\":3}
     _horizon_config_set $local_settings "" OPENSTACK_KEYSTONE_URL "\"${KEYSTONE_SERVICE_URI}/v3\""
 
+    # note(trebskit): if HOST_IP points at non-localhost ip address, horizon cannot be accessed
+    # from outside the virtual machine. This fixes is meant primarily for local development
+    # purpose
+    _horizon_config_set $local_settings "" ALLOWED_HOSTS [\"*\"]
+
     if [ -f $SSL_BUNDLE_FILE ]; then
         _horizon_config_set $local_settings "" OPENSTACK_SSL_CACERT \"${SSL_BUNDLE_FILE}\"
     fi