Fix ldap fixture and tls cert mounting for ci dind environments

This fix is necessary in order to not handle this case from CI where we modify GEM_HOME and install global gems in the build directory thus making CI setups inconsistent.

By creating tmp mount points in build directory, we ensure that mount points are accessible in all environment configuration without custom handling per job level

Related to refactor of nightly pipeline definitions: https://gitlab.com/gitlab-org/quality/pipeline-common/-/merge_requests/141