e2e-post-etna flake: Staking rewards test fails due to lack of funds

[marun]

failure of e2e-post-etna job has occurred a few times, symptom is delegator addition fails due to insufficient funds. Never seen this in pre-etna so presumably the test's assumptions about the funds required to perform the transaction are not accurate post-etna.

• https://github.com/ava-labs/avalanchego/actions/runs/11060123005/job/30729987908#step:5:2928
• https://github.com/ava-labs/avalanchego/actions/runs/11074121559/job/30772204550?pr=3337#step:5:2823
• https://github.com/ava-labs/avalanchego/actions/runs/11165631126/job/31037772777#step:5:3014
• https://github.com/ava-labs/avalanchego/actions/runs/11689509482/job/32552417648#step:5:2992

[Staking Rewards] should ensure that validator node uptime determines whether a staking reward is issued
/home/runner/work/avalanchego/avalanchego/tests/e2e/p/staking_rewards.go:36
  STEP: checking that the network has a compatible minimum stake duration @ 09/26/24 21:06:58.449
  STEP: adding alpha node, whose uptime should result in a staking reward @ 09/26/24 21:06:58.449
  Started ephemeral node "NodeID-LpX84YPS4NmkyrS6uLKrswhmecj7obAr3"
  STEP: adding beta node, whose uptime should not result in a staking reward @ 09/26/24 21:07:04.486
  Started ephemeral node "NodeID-GR4z11ZWQqhKJWhcGn7gHeThBjUFR4Yay"
  STEP: waiting until alpha node is healthy @ 09/26/24 21:07:10.448
  STEP: waiting until beta node is healthy @ 09/26/24 21:07:12.402
  STEP: retrieving alpha node id and pop @ 09/26/24 21:07:18.357
  STEP: retrieving beta node id and pop @ 09/26/24 21:07:18.358
  STEP: creating keychain and P-Chain wallet @ 09/26/24 21:07:18.359
   initializing a new wallet for node NodeID-LpX84YPS4NmkyrS6uLKrswhmecj7obAr3 with URI: http://127.0.0.1:34635/ 
  STEP: retrieving supply before adding alpha node as a validator @ 09/26/24 21:07:18.379
  STEP: adding alpha node as a validator @ 09/26/24 21:07:18.38
  validation period ending at: 2024-09-26 21:07:48.38025277 +0000 UTC m=+453.104296592
   issued transaction with ID: 2VP5X7TAimKeDJjF6iqCWrDVELJwKFxvomwGz923PuxJyYRbJV
  beta node validation period ending at: 2024-09-26 21:07:48.59572736 +0000 UTC m=+453.319771181
  STEP: adding beta node as a validator @ 09/26/24 21:07:18.595
   issued transaction with ID: i75Yx4FFjRLb4dKew1VqVjwkUUk3qYtDUcSqWL8qYTXJYaAix
  STEP: retrieving supply before adding gamma as a delegator @ 09/26/24 21:07:19.107
  STEP: adding gamma as a delegator to the alpha node @ 09/26/24 21:07:19.109
  delegation period ending at: 2024-09-26 21:07:34.109911548 +0000 UTC m=+438.833955368
   issued transaction with ID: 2kYzzVoYhyGzF1MGnc2ghE3z24dfH2YKnTxPBXCFwru87pK1PA
  STEP: adding delta as delegator to the beta node @ 09/26/24 21:07:20.419
  delegation period ending at: 2024-09-26 21:07:35.419336494 +0000 UTC m=+440.143380345
  [FAILED] in [It] - /home/runner/go/pkg/mod/github.com/stretchr/testify@v1.8.4/assert/assertions.go:1495 @ 09/26/24 21:07:20.426
  Test Metrics: https://grafana-poc.avax-dev.network/d/kBQpRdWnk/avalanche-main-dashboard?&var-filter=network_uuid%7C%3D%7Cf8fefb7f-6809-438f-99b5-05f1b9e53144&var-filter=is_ephemeral_node%7C%3D%7Cfalse&from=1727384818446&to=1727384852426
  shutting down ephemeral node "NodeID-GR4z11ZWQqhKJWhcGn7gHeThBjUFR4Yay"
  shutting down ephemeral node "NodeID-LpX84YPS4NmkyrS6uLKrswhmecj7obAr3"
• [FAILED] [22.281 seconds]
[Staking Rewards] [It] should ensure that validator node uptime determines whether a staking reward is issued
/home/runner/work/avalanchego/avalanchego/tests/e2e/p/staking_rewards.go:36

  [FAILED] 
  	Error Trace:	/home/runner/work/avalanchego/avalanchego/tests/e2e/p/staking_rewards.go:218
  	            				/home/runner/go/pkg/mod/github.com/onsi/ginkgo/v2@v2.13.1/internal/suite.go:323
  	            				/home/runner/go/pkg/mod/github.com/onsi/ginkgo/v2@v2.13.1/core_dsl.go:591
  	            				/home/runner/work/avalanchego/avalanchego/tests/fixture/e2e/ginkgo_test_context.go:46
  	            				/home/runner/work/avalanchego/avalanchego/tests/e2e/p/staking_rewards.go:198
  	            				/home/runner/go/pkg/mod/github.com/onsi/ginkgo/v2@v2.13.1/internal/node.go:463
  	            				/home/runner/go/pkg/mod/github.com/onsi/ginkgo/v2@v2.13.1/internal/suite.go:889
  	            				/opt/hostedtoolcache/go/1.21.13/x64/src/runtime/asm_amd64.s:1650
  	Error:      	Received unexpected error:
  	            	failed to decode client response: couldn't issue tx: flow check failed: insufficient unlocked funds: needs 1053 more 2Meaks6SE9btGsxri4UurLr3T4pHz6bzwTpzMkoZrKyWeHZNmJ