Pin packages in Dockerfile

Closes #59

See merge request openappstack/bootstrap!30

66 install apps

Closes #66

See merge request openappstack/bootstrap!32

improve behave

Closes #63

See merge request openappstack/bootstrap!29

Closes: #66

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

Closes #63

Related: #63

Resolve "Ensure netfilter-persistent is installed"

Closes #64

See merge request openappstack/bootstrap!31

Login test to keycloak

Closes #52

See merge request openappstack/bootstrap!27

On alpine:3.8 chromium (68.0.3440.75-r0) segfaults even when just using
`chromium-browser --version`. See
https://bugs.alpinelinux.org/issues/9161

alpine:3.9 shipps chromium 72.0.3626.109 which fixes the issue.

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