Actually I don't see laziness as a trait, but rather a behaviour. So I would say no, laziness is not an "INFP trait", insofar that it isn't "inherent" to the INFP's, or indeed any person's, being.
I think it's potentially damaging for people to define themselves by negative behaviours. I'm not saying it's inherently negative to sometimes choose relaxing and having a good time instead of "just going through the motions" every frickin' day or hour. But the behaviour that people refer to here (and that I'm all too familiar with), namely the "passive-aggressiveness towards working", I would say is indeed a negative behaviour. You're putting off a task that you know needs to be completed, so there you are, doing things which you can't fully enjoy because there's that nagging feeling you still have to complete the task at hand. You can try to suppress that nagging feeling and just do whatever you want, but ultimately it's going to bite you in the ass, unleashing a lot of negativity and whatnot.
When you start to identify with laziness, or other characteristics that are perceived as "negative", then it becomes difficult to deal with them because they're "part of you", and changing them implies you have to change the very core of your being.
That's another difficult and interesting question. Which traits are part of yourself and which other traits are disposable, can be changed without changing your core? This always fascinated me. What is someone's core? Does that even exist? Of course there's your genetic makeup, which imposes certain limits in which you can develop, and which maybe limit what you can become (although with increasing technology, these limits are becoming vaguer by the day). Then there's a little thing called neuroplasticity: oh, what wonderfully malleable brains we possess!
But before I stray too much off-topic, let me get to the point and finish the goddamn post. I think we all have, at least a "vague" idea of what makes us happy, or of what would make us happy. I also think that deep down, we know when we are wasting our time. Not from the perspective of society, but from our OWN perspective. Blundering about in a field collecting clovers may be perceived by most of the outside world as an outright waste of time, but if it truly makes you happy and you derive a true sense of fulfillment out of it, then you shouldn't fret.
However, sometimes there are mundane things which just seem to get in the way of our lofty dreams and visions... but we know that they have to be done, "or bad things will happen". Then it'll seem tempting to put off this task and sort of deny its existence for a while... but by doing this instead of confronting the task and relaxing and rewarding ourselves afterwards, we are wasting time. For example, I always had the habit of starting late on my homework, because the stress acted as a sort of "motor" to get it done. My results didn't suffer, I could do what I want, and I felt content, so there was no need to change this behaviour. In my first few years at university, the same strategy didn't work, I felt anxious and unfulfilled, both in my private as well as my academic life.
This is when we should look at 1) what makes us happy and 2) what needs to be done, and evaluate if what we are doing is conducive to both, or neither, and change our behaviour accordingly.