Consistently use 398 days for time variation rather than choosing

@infinity0

Hi! I am trying to remove some randomness from reprotest, to make it easier to consistently debug issues; e.g. getting different results between different runs of reprotest despite otherwise running in an identical environment.

I was wondering if you could comment on the logic with not varying the time in:

        if base < now - 15552000 and not random.randint(0, 1):
            # if ctx.base_faketime is far in the past, with 1/2 probability
            # reuse the current time and don't fake it

Maybe avoiding using faketime when otherwise the time since the previous build was long enough ago?

I am tempted to remove it entirely, but maybe I am missing something!

Removing the random probability codepath entirely might fix issues with some incompatibilities with faketime interaction with Makefiles and quilt applied patches from debian/patches/ ... further research needed.