don't reset if already gated

[etuleu]

Sometimes when goal engaged, for some reason, VS gates again, which resets the effort. We don't want that to happen in this case. We only want it when engaging in a goal.

[codecov[bot]]

Codecov Report

Patch coverage has no change and project coverage change: -0.01 :warning:

Comparison is base (95f683a) 30.10% compared to head (62d0533) 30.10%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #276 +/- ## ========================================== - Coverage 30.10% 30.10% -0.01% ========================================== Files 85 85 Lines 15282 15283 +1 ========================================== Hits 4601 4601 - Misses 10421 10422 +1 Partials 260 260 ``` | [Impacted Files](https://app.codecov.io/gh/emer/axon/pull/276?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=emer) | Coverage Δ | | |---|---|---| | [axon/pvlv.go](https://app.codecov.io/gh/emer/axon/pull/276?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=emer#diff-YXhvbi9wdmx2Lmdv) | `53.93% <0.00%> (-0.31%)` | :arrow_down: |

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