fix(operator): Fix take to complete when the source is re-entrant.

[trxcllnt]

Description:
The TakeSubscriber compares the instance variable count to determine if it should complete or not.

If the source Observable is re-entrant, this check fails (because count is updated in each next), and take never completes.

I encountered this issue with expand and take on a multicast Observable, but here's a much simpler repro example:

import { Subject } from 'rxjs';

const subject = new Subject();

subject
  .take(10)
  .subscribe(
    (i) => {
      console.log(i);
      subject.next(i + 1);
    },
    (err) => {},
    () => console.log('done') // never gets printed
  );

subject.next(0);

[coveralls]

Coverage increased (+0.0005%) to 97.001% when pulling 86615cb on trxcllnt:fix-re-entrant-take-completion into 646b38d on ReactiveX:master.

[kwonoj]

LGTM

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.