serverutil/perm: minor cleanup of unused variables
serverutil/perm: minor cleanup of unused variables

Tests still pass.
No new lint or vet errors.

Change-Id: I2d2e99d8fe13553c1abf17925bd859780cec7b25
Reviewed-on: https://upspin-review.googlesource.com/7803
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@google.com>

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