Move smartcard validation being done by qemuBuildSmartcardCommandLine()
to the existing qemuDomainSmartcardDefValidate() function. This
function is called by qemuDomainDeviceDefValidate(), allowing smartcard
validation in domain define time.

Tests were adapted to consider the new caps being needed in
this earlier stage.
Reviewed-by: NCole Robinson <crobinso@redhat.com>
Signed-off-by: NDaniel Henrique Barboza <danielhb413@gmail.com>