clear all cache before render

@rodlie Hi man. Is it a good idea to command a clear all cache before rendering job starts automatically?

The thing is I have found some projects with gpu nodes tend to break apart if cache exists and while rendering this broken images are going to be rendered. For safety check I am clearing all cache with ctrl+shift+k before starting the final render. Seems to be working good and error free.

But users including me often forget about it. So, may be better clearing it automatically?