ansible: add AWX install

[AshCripps]

Currently a WIP, I have a server up and running created from this playbook I just need to:

• set dns
• set up passwords/secrets

I have also added a restart agent playbook which i will fill out with my OS/ARCHS which will be a sample that the build helpers can run themselves.

refs: #1390 (Old PR)

[AshCripps]

@richardlau can you change the preexisting dns entry from ansible tower to point to 169.60.150.91 please

[richardlau]

I've updated the dns entry for ansible from 169.62.77.235 to 169.60.150.91.

[AshCripps]

The DNS is now working properly at ansible.nodejs.org. Next step is to get the github login working that ive requested at nodejs/admin#620

[AshCripps]

Think this is ready to review in terms of working for the build helper side of things - all thats missing is the github auth and maybe a README on manual setup.

[AshCripps]

@nodejs/build can I get some reviews on this? particularly around the new playbooks Ive made for the build-helper role just to make sure everyone is comfortable with them. (e.g. the clear workspace one isnt too aggresive)

After that I can merge and redeploy to instance ready for others to use

[Trott]

I am Not Great with ansible, but it looks good to me.

[rvagg]

Probably fine for a start. I assume we're going to have good docs for this? I wouldn't want to see this run (a) while jobs are actively running and (b) on certain machines (like the Pi's—it can be done, but the costs are great so I wouldn't want to encourage casual cleanup of them).

These can come later but I wouldn't mind expanding the list too to cover the tmp directories, and then the directories that citgm ends up making.

I regularly clear out /home/iojs/tmp/, /home/iojs/node-tmp/, but they often contain dotfiles which are annoying to remove without .. accidents.

citgm ends up cluttering up a lot of other stuff that it's nice to clean occasionally - .standard, .npm, .node-gyp, .cache, .yarn, .. I can't recall exactly but there's a whole list i regularly clean out when I see it.

[AshCripps]

@rvagg Ill make sure I write up some more docs to make at clear as possible before roll out, atm its only working at test hosts because that the only credential I added (also the only level I felt comfortable with) but I can look into removing the Pis if will feel they would be troublesome to manage this way.