fix: build: set PropagationDelaySecs correctly

[arajasek]

Related Issues

The global field wasn't actually being set (just a local variable).

Proposed Changes

Set the field correctly.

Additional Info

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[Reiers]

export PROPAGATION_DELAY_SECS=8

2022-09-22T18:12:08.043+0200	INFO	miner	miner/miner.go:475	completed mineOne	{"tookMilliseconds": 14, "forRound": 1326745, "baseEpoch": 1326744, "baseDeltaSeconds": 8, "nullRounds": 0, "lateStart": false, "beaconEpoch": 0, "lookbackEpochs": 900, "networkPowerAtLookback": "3587328484311040", "minerPowerAtLookback": "0", "isEligible": false, "isWinner": false, "error": null}

export PROPAGATION_DELAY_SECS=12

2022-09-22T18:15:12.478+0200	INFO	miner	miner/miner.go:475	completed mineOne	{"tookMilliseconds": 3, "forRound": 1326751, "baseEpoch": 1326750, "baseDeltaSeconds": 12, "nullRounds": 0, "lateStart": false, "beaconEpoch": 0, "lookbackEpochs": 900, "networkPowerAtLookback": "3587328484311040", "minerPowerAtLookback": "0", "isEligible": false, "isWinner": false, "error": null}

[arajasek]

Dealing with the flaky test failure in #9061