timer: call list.start regardless new or not

[Aminadav]

Pull Request check-list

Please make sure to review and check all of these items:

• Does make -j8 test (UNIX) or vcbuild test nosign (Windows) pass with
  this change (including linting)?
• Is the commit message formatted according to CONTRIBUTING.md?
• If this change fixes a bug (or a performance problem), is a regression
  test (or a benchmark) included?
• Is a documentation update included (if this change modifies
  existing APIs, or introduces new ones)?

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Affected core subsystem(s)

Please provide affected core subsystem(s) (like buffer, cluster, crypto, etc)

Description of change

Please provide a description of the change here.

Call start regardless whether list is new
or not to prevent incorrect active_handles
count.

Fixes nodejs/node-v0.x-archive#25831