node: Fix time since last block.

[winder]

Summary

We started skipping the last round timestamp and synced since timestamp with a recent change.

Test Plan

New e2e test.

[Eric-Warehime]

LGTM once your test passes.

[codecov]

Codecov Report

Merging #5113 (5faa106) into master (6487b37) will increase coverage by 0.01%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #5113      +/-   ##
==========================================
+ Coverage   53.42%   53.43%   +0.01%     
==========================================
  Files         431      431              
  Lines       54369    54381      +12     
==========================================
+ Hits        29046    29058      +12     
- Misses      23061    23066       +5     
+ Partials     2262     2257       -5     

Impacted Files	Coverage Δ
node/follower_node.go	24.86% <0.00%> (-0.84%)	⬇️
node/node.go	4.10% <0.00%> (-0.04%)	⬇️
ledger/blockqueue.go	82.25% <0.00%> (-2.69%)	⬇️
ledger/testing/randomAccounts.go	55.65% <0.00%> (-0.62%)	⬇️
network/wsNetwork.go	64.98% <0.00%> (-0.19%)	⬇️
catchup/service.go	69.17% <0.00%> (+0.23%)	⬆️
ledger/acctonline.go	79.16% <0.00%> (+0.52%)	⬆️
ledger/acctupdates.go	69.72% <0.00%> (+0.72%)	⬆️
ledger/catchpointtracker.go	58.69% <0.00%> (+0.78%)	⬆️
catchup/peerSelector.go	100.00% <0.00%> (+1.04%)	⬆️
... and 1 more

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[mciccarello]

Looks ok to me.

[algojack]

lgtm, thanks for fixing it.