[dts] [PATCH V1] framework/crb: modify code logic

[Tu, Lijuan]

> Code 'os.path.isfile()' only be executed locally(tester side), lead to recovery ENV
> fail.
> The code logic is to judge files on DUT, so change it as below.
> 
> Signed-off-by: Jianwei Mei <jianweix.mei at intel.com>

Applied