OCFS2: edit FAQ. Add doc links

[trispera]

Proposed changes

Briefly describe the changes you've made here. Remember to add a link to the preview page of your branch.

https://csc-guide-preview.rahtiapp.fi/origin/multi-attach-updates/cloud/pouta/multiattach

Checklist before requesting a review

• [x] I have followed the instructions in the Contributing and Styleguide documents.
• [x] My pull request passes the automated tests. (If not, visit pull requests at Travis CI and have a look at the job log.)
• [x] I have included a link to the appropriate preview page (select your branch from the list).