Modify if statement to choose appropriate cbfs/kernel
Modify if statement to choose appropriate cbfs/kernel

Modify the kernel choose logic, when cbfs exists, use it first in any
situation; else if kernel exists, use it; if nothing exists, report
error.

Signed-off-by: Zhang Wei <14976e959b2860fb06a3c1edbdb1945a4e11b8b5@huawei.com>

laijs/runv,gnawux/runv,jinfenw/runv,hyperhq/runv,hyperhq/runv,laijs/runv,bergwolf/runv,hyperhq/runv,gnawux/runv,jinfenw/runv,gao-feng/runv,jinfenw/runv,gao-feng/runv,laijs/runv,gao-feng/runv,gnawux/runv,bergwolf/runv,bergwolf/runv