Fix reschedule issue with same callback

[Dimon4eg]

The issue:

• create timer with some repeat count
  cc.director.getScheduler().schedule(callback, target, interval, repeat, delay, paused, key);
• wait for last repeat executed
• in timer callback reschedule it again with the same callback
• as result timer is broken and will never be executed

Reason:
When we reschedule timer again from callback the scheduler just updates interval value:
timer._interval = interval;

After callback executed timer will be canceled:

if (this._callback && !this._runForever && this._timesExecuted > this._repeat)
     this.cancel();

Fix:
Scheduler will update interval only for not exhausted timers (still running).
In our case, it will create new internal timer object and old one will be canceled after callback.

[Dimon4eg]

Please don't merge yet. I'll sync it with PR for cocos2d-x

[dumganhar]

@Dimon4eg ， could this PR be ready for merge now?

[Dimon4eg]

Done. Also added test for this issue in cocos2d-x repo.

[minggo]

@dumganhar any question about the issue?

[Dimon4eg]

@dumganhar any update?
The same fix already has been merged to C++ engine cocos2d/cocos2d-x#17706