target-i386: Check for host features before filter_features_for_kvm()

commit 5ec01c2e96910e1588d1a0de8609b9dda7618c7f broke "-cpu ..,enforce",
as it has moved kvm_check_features_against_host() after the
filter_features_for_kvm() call. filter_features_for_kvm() removes all
features not supported by the host, so this effectively made
kvm_check_features_against_host() impossible to fail.

This patch changes the call so we check for host feature support before
filtering the feature bits.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Message-id: 1364935692-24004-1-git-send-email-ehabkost@redhat.com
Cc: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
