key storage non-default dir path support

[rooty0]

This feature allows to modify path of the key storage directory. (The Key Storage container allows storing public keys, private keys, and passwords)

related discussion: https://groups.google.com/forum/#!topic/rundeck-discuss/fzrQ26USTPU

[liamjbennett]

The context for this change: http://rundeck.org/docs/administration/storage-facility.html

[liamjbennett]

While I think this is a perfectly good change. I'm wondering if we can make it more generic and provide support for configuring other storage plugins as well.

[rooty0]

hey @liamjbennett, yeap, I was thinking about that, but that change (storage plugins) will be as a different task, need to spend some time on that.

This PR is just a quick fix-feature for non-standart key storage path support.
I can give a real life example.
I'm using rundeck within AWS and all data (like database, logs) should be on EBS, in my case it's "/rundeck". So I was able to change path almost for every resource. The only one thing that left - Key storage. What I understood from discussion with Greg, this PR is the only way to do that.

[liamjbennett]

Ok, sounds reasonable.