Wrong proxy port in nova.conf for Spice proxy

If we look at nova/cmd/spicehtml5proxy.py, we use 6082 port for Spice proxy.

In nova.conf, the default port for html5proxy_base_url is 6080 which fails console
service.

Fix bug #1172957
Cherry-picked from https://review.openstack.org/#/c/27524/

Change-Id: I52ca37f76e7a6abd085b079ae42e7914cb619ad5
Merge "Wrong proxy port in nova.conf for Spice proxy" into stable/grizzly