Changing default setting as "allowed_hosts=*"

Currently we are getting support issues as HUE in following configuration generates "400 Bad Request" error.

1. When HUE's django server started on IP:PORT
e.g. hue runserver IP:PORT

2. When HUE is hosted on AWS(with ec2 domain name) and clients are coming from different domain names

In above cases if default HUE setting is "allowed_hosts=[".domainname"]" which can created DOS(denial of service) from HUE.

When default setting is changed to allowed_hosts=["*"] above DOS can be prevented.

Also with this user can still put "allowed_hosts" settings and HUE will reflect it.