add vagrant docker provider

Signed-off-by: rootfs <hchen@redhat.com>
add vagrant docker provider

Signed-off-by: rootfs <hchen@redhat.com>
review feedback

Signed-off-by: rootfs <hchen@redhat.com>
validate if vagrant provider is as expected

Signed-off-by: rootfs <hchen@redhat.com>
create ssh key for vagrant ssh to consume

Signed-off-by: rootfs <hchen@redhat.com>
Merge pull request #528 from rootfs/vagrant-docker

add vagrant docker provider