virDomainCreate(XML)WithFiles: Add check for VIR_DRV_FEATURE_FD_PASSING

virDomainCreate(XML)WithFiles: Add check for VIR_DRV_FEATURE_FD_PASSING

All APIs using FD passing have this check to prevent sending a
'VIR_NET_CALL_WITH_FDS' to an older daemon but
virDomainCreateXMLWithFiles was missing it.

Now the LXC driver was historically not exposing
VIR_DRV_FEATURE_FD_PASSING, but that is not a problem as LXC always goes
through the remote driver which intercepts it and injects
VIR_DRV_FEATURE_FD_PASSING when it was implemented.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>