Vagrant >1.7 is unable to login to the default boot2docker host if it has
been halted and brought back up again.
This is because the insecure SSH keypair is replaced but boot2docker doesn't
persist filesystem changes between reboots. So when next brought up Vagrant
tries to use the new keypair which is no longer valid and subsequently isn't
able to login.
Prevent this from happening by disabling the `ssh.insert_key` option on
versions where it is available.
Initial work
commands/up: make sure all names to with_target_vms are strings
providers/docker: create a docker host VM if needed
providers/docker: executor abstraction for driver to eventually support remote
providers/docker: vagrant executor
providers/docker: support creating the machine
providers/docker: status works if host VM is gone
providers/docker: use start fence to get real docker output
core: Call preserves stack ordering
core: support Message post option
providers/docker: Guard some features with HasSSH checks
providers/docker: much better messaging around create/destroy
providers/docker: output the container ID on create
providers/docker: copy the hostmachine Vagrantfile to the data dir
providers/docker: should make host machine before any up action
providers/docker: HandleBox before the host machine
providers/virtualbox: functional_vboxsf to disable vboxsf
providers/virtualbox: synced folder usable method should take 2 args
providers/docker: default machine name to :default
Mitchell Hashimoto
Dan Carley