Mount secrets.yml to dependencies initContainer

Closes #1815 (closed)

There are situations where db:version (which is what wait-for-deps script in dependencies initContainers does) requires the secrets stored in secrets.yml, without which they fail to decrypt data. We are already mounting them to /etc/gitlab/rails-secrets/secrets.yml in the initContainers, but not to /srv/gitlab/config/secrets.yml.