guests/openbsd: OpenBSD is not a Linux derivative
guests/openbsd: Add back `insert_public_key` cap

Copied from linux guest.
provisioners/docker: always pull images [GH-2901]
kernel/v2: test for some config
kernel/v2: more tests
kernel/v2: support overriding provisioner settings
kernel/v2: support merging properly
website/docs: document it
kernel/v2: support the preserve_order option (documented)
Fix typo in sentence
provisioners/docker: configuration is mergeable
provisioners/puppet: mergeable config
kernel/v2: finalize the provisioner configs
Merge pull request #2929 from mitchellh/f-provisioner-id

Provisioner Inheritance/Overriding

This allows provisioners to be overridden by sub-scopes (machine configs, provider overrides), allowing common provisioning to be put into the global scope and selectively overriding certain configurations. This allows for getting rid of a lot of duplication without having to know a lot of Ruby.

Completely documenting in the pull request (in website/docs commits), so read there.
Update CHANGLEOG
Merge pull request #2930 from danielbachhuber/fix-typo

core: fix typo in sentence
guests/openbsd: Ensure that `PKG_PATH` is set when installing rsync

Depending on the shell, `PKG_PATH` is not necessarily set when Vagrant
runs `pkg_add`.

Ref: GH-2917
Merge pull request #2892 from tmatilai/openbsd

OpenBSD is not a Linux derivative
kernel/v2: fix provisioner config with blocks

Regression from 10d5416.