RackHD support

[chungers]

This PR moves the code from the Dell/EMC RackHD infrakit plugin into the main infrakit repo and make the plugin a built-in that can be started up with infrakit plugin start rackhd.

• Moved the plugin source code into pkg/provider package namespace and preserved commit history
• Code changes to make the plugin compile and build
• Temporarily disabled tests since 3 tests are failing (TODO)
• Made the options in the rackhd plugin package exported / public so that we can set the options in configuration JSONs.
• Added driver code so that the rackhd plugin can be started with the CLI infrakit plugin start and as rackhd kind.

CC - @spiegela @ajeetraina

Signed-off-by: David Chung david.chung@docker.com

[GordonTheTurtle]

Please sign your commits following these rules:
https://github.com/moby/moby/blob/master/CONTRIBUTING.md#sign-your-work
The easiest way to do this is to amend the last commit:

$ git clone -b "rackhd" git@github.com:chungers/infrakit.git somewhere
$ cd somewhere
$ git rebase -i HEAD~842353608520
editor opens
change each 'pick' to 'edit'
save the file and quit
$ git commit --amend -s --no-edit
$ git rebase --continue # and repeat the amend for each commit
$ git push -f

Amending updates the existing PR. You DO NOT need to open a new one.

[codecov]

Codecov Report

Merging #698 into master will decrease coverage by 1.37%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master     #698      +/-   ##
==========================================
- Coverage   50.02%   48.65%   -1.38%     
==========================================
  Files          80       82       +2     
  Lines        8653     8897     +244     
==========================================
  Hits         4329     4329              
- Misses       4008     4252     +244     
  Partials      316      316

Impacted Files	Coverage Δ
...der/codedellemc/rackhd/plugin/instance/instance.go	0% <0%> (ø)
...ider/codedellemc/rackhd/plugin/instance/builder.go	0% <0%> (ø)
pkg/x/remoteboot/remoteboot.go	20.25% <0%> (+0.08%)	⬆️

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