TestTimerResets flaps when run with race detector

[zwass]

Not always, but typically using -count 100 is sufficient to see a few failures:

$ go test -race -run TestTimerResets -count 100
--- FAIL: TestTimerResets (0.05s)
	mock_test.go:14: expected timer to get after reset when interval is up after restarted
--- FAIL: TestTimerResets (0.05s)
	mock_test.go:14: expected timer to get after reset when interval is up after restarted
--- FAIL: TestTimerResets (0.05s)
	mock_test.go:14: expected timer to get after reset when interval is up after restarted
FAIL
exit status 1
FAIL	github.com/mixer/clock	3.573s

[connor4312]

THanks for the issue! I'll try to take a look at this soon.

[zwass]

I should note that I have not noticed any problems due to this besides the test failure, so from my perspective it is not urgent. Thank you!