publish-failsafe-error-promise and promise-key-download-url-ready shall be
less reactive, as otherwise it results with constant problems detection on
the running cluster, by raising tickets. When those promises are less
sensitive it gives time for the cluster to stabilize.

Make it possible to mock any specific cron entry.

Those are candidates to be shared by some other place, like slapos testing.

See merge request nexedi/slapos!1693

Following advice from https://luajit.org/download.html use recent commit id,
but rely on github archive.

Drop obsoleted patch, enforce --with-shared-termcap-library

Also use directly archive with patches.

Changes:
 * use xz archive
 * stabilize patch name
 * update patch to current version