kola/tests/locksmith/locksmith: Make coreos.locksmith.tls more robust

[pothos]

On VMware ESXi there were reproduceable test failures with kola due to
the certificate date ("certificate is not yet valid") but these
failures were not reproducible by executing the same commands manually.
Cover the failing command in a rety loop because I suspect that the
system time got slightly adjusted or something similar in between
which causes the certificate to be invalid for a short time.

How to use/test

./cork download-image --cache-dir=tmp --json-key=/dev/null --platform=esx --root=gs://flatcar-jenkins/beta/boards/amd64-usr/2513.2.1
./ore esx --esx-config-file esx.json remove-vms
./kola run -d --esx-config-file esx.json --esx-ova-path tmp/flatcar_production_vmware_ova.ova --parallel=4 --platform=esx --channel=beta --tapfile=vmware-esx.tap coreos.locksmith.tls

[t-lo]

LGTM, please merge and re-run the coreos.locksmith.tls test on vmware.