tests: add pxe e1000 and virtio-pci tests The test is based on bios-tables-test.c. It creates a file with the boot sector image and loads it into a guest using PXE and TFTP functionality. Cc: Jason Wang <jasowang@redhat.com> Signed-off-by: Victor Kaplansky <victork@redhat.com> Suggested-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>