webadmin: minor cleanup in SpiceConsoleModel

Replace statements that check the versions of spice-driver or
guest-agent in a VM in order to see if the VM has spice-driver
or guest-agent installed with calls to VM#getHasSpiceDriver and
VM#getHasAgent methods

Change-Id: Iad08ac04476defcfa0d53443390f762f023de96f
Signed-off-by: Arik Hadas <ahadas@redhat.com>