Use Ice.Default.Host if available (Fix #12424)

See:
 * https://trac.openmicroscopy.org.uk/ome/ticket/12424
 * https://www.openmicroscopy.org/community/viewtopic.php?f=5&t=7546&p=14200#p14200

To test:
 * issue `bin/omero config set Ice.Default.Host youriphere`.
 * OMERO should be listening on this interface if checked via `netstat -na | grep 4064`
 * The output of `bin/omero web -h` should show `omero.web.server_list` pointing to this interface.
 * It should be possible to login to the web with no special configuration.

/cc @chris-allan, @aleksandra-tarkowska, @will-moore, @dpwrussell, @manics, @bpindelski

Question: Is there any reason that the Django application host defaults to `0.0.0.0` and can't use the same interface as `server_list`?
```
    "omero.web.application_server.host": ["APPLICATION_SERVER_HOST", "0.0.0.0", str],
```