frontend: force admin-console only on AdminPortal

In RHEV 3.1, the UserPortal discovered to force the AdminConsole which is not
expected behavior and will cause the 3.0 spice client to not auto-adjust to the
client's screen resolution.

Steps to Reproduce:
1. Install RHEV 3.1
2. Continue to use 3.0 spice-client
3. Open UserPortal
4. Connect to Spice console

Fixed by setting the AdminConsole flag in UserPortal properly.

Change-Id: I6a5cefd4ba86bdad46851381c1973141e19979ff
Signed-off-by: Frantisek Kobzik <fkobzik@redhat.com>