frontend: disable spice options in instance types

This patch disables the spice settings added in commit
662f6fa8d26409be4e4c4b835e29a61e20d20244

And wrongly left partially enabled.

Change-Id: I6c8cd0ecb84e21c5406cbb6bc4950cb8537645b0
Bug-Url: https://bugzilla.redhat.com/??????
Signed-off-by: Francesco Romani <fromani@redhat.com>