Support index.unassigned.node_left.delayed_timeout

[andrewthad]

After the big refactor is done, I'd like to add support for index.unassigned.node_left.delayed_timeout to UpdatableIndexSetting. The default value of 1m that elasticsearch uses is bad, and in my own cluster, I set this to 10m so that restarting a node doesn't make elasticsearch decide to start relocating a bunch of stuff before it comes back up.

[bitemyapp]

so that restarting a node doesn't make elasticsearch decide to start relocating a bunch of stuff before it comes back up.

Urgh, I've seen this before too. I'll try to get things wrapped up.