Sometime fetching LE certs take up to 23mins,
see https://code.greenhost.net/openappstack/bootstrap/issues/90#note_48508

Fixes #98

This happened randomly in the past, see
https://code.greenhost.net/openappstack/bootstrap/merge_requests/36#note_47928

CI_PIPELINE_ID is exposed in gitlab CI web interface,
so droplets are more easy to debug.

By this we can run tests with testinfra while waiting for
LE certs to get served.

Closes: #53

Two concurent docker jobs can't fetch the same cache, see
https://gitlab.com/gitlab-org/gitlab-runner/issues/1151

Closes #63

Related: #63

See #60 for details.
For Ci droplets we use LE staging CA, so we need to provide curl
with the CA cert. Surprisingly, curl will still validate certs from
LE production CA even if "--cacert=./letsencrypt_fakelerootx1.pem" is
used.

See #53