[5.3] Cache: fix file store extending cache expiration time

[zoltanpeto]

Problem: When incrementing a cached value which expires in less than a minute, the expiration time is extended to a full minute. This mainly causes problems when using API rate limiter with file cache driver, see #15152.

Solution: don't round up the remaining number of minutes when retrieving cache payload, cast calculated seconds to int in expiration() instead.

Other cache drivers don't seem to have this problem.

[zoltanpeto]

I'm wondering if this could be merged into 5.1/5.2 also, I don't think it would be a breaking change - I only based this case on 5.3 because @GrahamCampbell advised me to in #15152. Thoughts?

[taylorotwell]

I suggest not using file cache in a production scenario really.