Update gitlab.rb.erb in bosh release templates for 9.0 (Releasing Tile v1.2.0), Update package to 9.0.6-ee.0

The embedded gitlab.rb.erb template for Omnibus-GitLab hasn't actually been upgraded for close to a year, and a lot of possible changed have occurred inside the original since then. Bring this up to date, and translate any changes forward, removing anything that might cause a problem with 9.0 plus with deprecations, etc.

• Update gitlab.rb.erb to GitLab 9.0 series
  • Disable PostgresQL (ensure)
  • Disable Redis (ensure)
  • Disable Mattermost (confirm)
  • Disable Pages
  • Disable Exporters for Prometheus
    • Redis
    • PostgresQL
    • node-exporter
    • GitLab Monitor (?)
  • Disable Gitaly (ensure)
  • Disable GitLab Sentinel (ensure)
  • Disable Container Registry (limitation of CF router)
• Omnibus needs bumped to version gitlab-ee-9.0.6-ee.0

cc @marin