qemu: Add a multi_vms_file_transfer dedicated file

So we can run it outside the sr-iov context.
Signed-off-by: NLucas Meneghel Rodrigues <lmr@redhat.com>

qemu/tests/cfg/multi_vms_file_transfer.cfg

+- multi_vms_file_transfer:
+    only Linux
+    type = multi_vms_file_transfer