make possible to reduce fluky tests

[kamilsk]

--- FAIL: TestBreakBySignal (0.00s)
    --- FAIL: TestBreakBySignal/with_signal (0.02s)
        breaker_test.go:216: max difference between 2021-01-24 21:27:21.89766 +0300 MSK m=+0.017424561 and 2021-01-24 21:27:21.908426 +0300 MSK m=+0.028190544 allowed is 10ms, but difference was -10.765983ms
FAIL

$ make test
--- FAIL: TestMultiplexThree (0.01s)
    deprecated_test.go:30: a breaker is not released
    deprecated_test.go:30: a breaker has inconsistent state
    deprecated_test.go:30: a breaker has no error
FAIL
FAIL    github.com/kamilsk/breaker      0.884s
FAIL
make: *** [test] Error 1

[kamilsk]

It shows fundamental error: if Done is closed, the Err must return Interrupted, but it is undefined, because released int32 stores 1 only if goroutine is released