Skip uuu deploy/boot if uuu_usb_otg_path not defined.
We plan to add UUU to healthy check job to let it automatically recover uboot if some device was broken.
But in local, there is some device not directly link to lava slave, but link to a serial console server. However, lava dispatch device base on devicetype which will make some device's healthy check failure. So add this patch to let device has the ability to skip UUU boot for these devices not directly link to lava slave: that is not define "uuu_usb_otg_path" in device jinja2 file.