Persistence test is failing on Linux during Docker image build

[biozz]

test_persist is failing when the image is built on Linux. It builds successfully on a Mac with buildx and a cross-platform build.

This works on an M1 Mac: docker build -t rustpad:latest --platform=linux/amd64 .

This doesn't work on amd64 Ubuntu 20.04: docker build -t rustpad:latest .