Add support for high_availability parameters

GitLab omnibus 7.1+ now supports the ability to ensure that a mountpoint exists before starting services. This is exposed in the gitlab.rb as:

high_availability['mountpoint'] = /path/to/mount/point

Can the gitlab.rb template be updated to include support for the high_availability parameter(s)? Here's some information on the feature: gitlab-org/omnibus-gitlab!163 (diffs)

Thanks.