Avoid allocation storing last active time

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 79.13%. Comparing base (d30f13f) to head (f8de116).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #690 +/- ## ========================================== - Coverage 79.15% 79.13% -0.03% ========================================== Files 41 41 Lines 3733 3733 ========================================== - Hits 2955 2954 -1 - Misses 548 549 +1 Partials 230 230 ``` | [Flag](https://app.codecov.io/gh/pion/ice/pull/690/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pion) | Coverage Δ | | |---|---|---| | [go](https://app.codecov.io/gh/pion/ice/pull/690/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pion) | `79.13% <100.00%> (-0.03%)` | :arrow_down: | | [wasm](https://app.codecov.io/gh/pion/ice/pull/690/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pion) | `22.16% <100.00%> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pion#carryforward-flags-in-the-pull-request-comment) to find out more.

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