Add the api config opts in groups to deal with the single heat.conf

Add the api config opts in groups to deal with the single heat.conf

So first off, I also don't like the replicating of the api_opts in wsgi.py
but if I don't do that the sample generator doesn't work:(

We add the wsgi options into a group for each of the api servers with
the deprecated group of "DEFAULT" so it still deals with the flat layout.

The behaviour is as follows (assuming heat-api):
1) if you have both (/etc/heat/{heat.conf, heat-api.conf}
   the value in heat-api.conf wins over heat.conf
2) if you have just one of the config files but a value in both the
   [DEFAULT] section and the [heat-api] section then the value in heat-api
   wins.

bug #1209141
Change-Id: I66ddb3dca91d13b28e68dfb4306e94eb4e537fa7