Add Blocking

[Smithx10]

I find myself writing the following often. I'm curious if there would be way to block until the desired action is complete similar to the -w option in node-triton. Or if CloudAPI could be enhanced to track this better?

-w, --wait  Wait for the creation to complete. Use multiple times for a
                spinner.

err = c.waitForInstState(cmpt, instUUID, "running", 60)

[twhiteman]

This is something that has annoyed me for a while - a job/wait style of API (or maybe exposing workflow jobs through CloudAPI) would be good. E.g.
https://smartos.org/bugview/TRITON-2076

Note that the node-triton waits are generally looking for changes on one specific property (e.g. vm.state changing).

[Smithx10]

@twhiteman I was thinking one way to solve this is to expose the internal change feed events for certain things over a websocket for only that account. The following branch has some rough work to make this happen we could than use that in triton-go to block etc. TritonDataCenter/sdc-cloudapi@master...Smithx10:changefeed