Timer cancellation is not reliable

We detect whether the timer was canceled in ad-hoc ways.
Especially, if a lock is involved, the situation is not desirable.
This commit addresses that: https://github.com/CodeChain-io/codechain/commit/96f7f942f3021b4154a5da14bbd7680c1e080200

We need a regular mechanism to know fired timeout is canceled, not by ad-hoc devised ways if we can't control it.